Sorry for the late update. I've been really busy.
A lot of things have changed and I'm still working on the wiki.
If you have any questions you can join the discord server or DM me on Spigot (note that I'm a new dev working on the plugin you should DM @CryptoMorin not Hex).
1.8 is not fully tested, let me know if it works.

Make sure to take a backup of your Skills folder before updating.


New:

• 1.15 Support
• 1.8-1.15 Material and Sound support.
  
• Party system is completely removed and replaced with Parties plugin support.
• Added TAB Completer for commands.
• Help page now shows the total page numbers next to the page number.
• You can now check how many EXP you need to level up in /Skills level
• Added /Skills setskill <skill> command syntax.
• /Skills setskill will now check if the player has any saved data.
• Added the following placeholders: %skills_def%, %skills_str%, %skills_dex%, %skills_int%, %skills_rawxp%. Some placeholders are also changed.
• You can now use short_ before any integer placeholders to convert it to a short number. E.g. %skills_short_soul% 2854 -> 2.8K
• You can now do /skills select if you have already have a skill and have skills.select.override permission.
• Added a new equation for leveling system. This one is much more smarter.
• Merged /Skills see <player> with /Skills info <player> with permission skills.info.others and a message in the language file.
• Changed message colors.
• A lot has changed in the config.yml please reset it.
• You can now specify a type of mob for mob souls and mob exp in config TYPE:<mobtype>, <amount> e.g. TYPE:ZOMBIE, 7
• You can now downgrade mastery by right-clicking on it. However there's a permission for it if you want it added. So players can't keep their souls after dying.
• You can now edit online/offline/leader prefix in language file.
• You can now use lose-same-souls-as-killer-souls-gain feature.
• Arbalist arrows are no longer automatically removed. I find it cooler this way myself. If anyone wants it disabled, I'll add an option.
• Added the Stats Point explanation in the item's lore instead of displaying a message in /Skills stat
• You can now specify the material types as well as the dropped material, its amount and the chance for Logging mastery from mastery-logging-materials option.
• Removed old Skill Improvement config converter.
• You can now change the skill items (not for the GUI) in the config skill-item.<skill>
• Merged Skills Strength and Weakness with its Description.
• You can now choose the item's name and material for skills in /Skills select
• Replaced HTML styled <br> line separator with the new line escape \n character.
• Language file will now use one line only as the multi-line was completely useless. You can use \n for new lines.
• Masteries GUI now uses 5 slot columns to fit the masteries count.
• You must reset your config and language file. The plugin will automatically backup the ymls files if you haven't reset them.
• Added SavageFactions support.
• Added an update checker.
• Config handler is recoded and should run more smoothly.
• You don't need to install ActionBarAPI plugin anymore, it's built-in.
  
• ActionBar is now completely customizable.
• ActionBar now uses animations energy.
• ActionBar now updates every one second (instead of 1.5 seconds) using async Tasks. It's improved.
• Skills Loss message is no longer shown if the lost souls are 0.
• Now the language file doesn't spam in console if it's the first time loading the plugin.
• What's the most retarded thing you can do with a Minecraft plugin?

Fixed:

• Saves reloads all the loaded player data on /Skills reload.
• No more IOException Stackoverflow when players folder isn't found.
• JSON data files now have the ".json" file extension... And it no longer saves unnecessary data such as the id and uuid (player's name and UUID) in the data file.You don't need to worry about your player data, they're automatically converted. It also backups data automatically before converting in players/backup folder.
• PlaceholderAPI will now use the Expansion API instead of Ez API. Please update your PlaceholderAPI to the latest version.
• Fixed an issue with help page throwing error on wrong page numbers.
• Fixed an issue with pages showing duplicated commands.
• Plugin is actually going to disable now after the, "Could not initiate LanguageSupport. Plugin is going to be disabled." error.
• Command usage messages will now follow <required> and [optional] argument format.
• Party permissions changed from the format skillsparty.<permission> to skills.party.<permission>
• You can now use spaces for lists in the config between each comma blah,blah -> blah, blah
• Fixed drowned spawner farming. Thanks to
• Fixed clicks being called two times (duplicated messages and etc.) in 1.9 and above.
• Fixed a problem with item lore in the language file not passing the last color to the next line. And now it listens to <br> separator properly.
• Stats (health) will now update on levelup.
• Fixed an error when the plugin couldn't load and disabled itself for any reason.
• You can now get skills (_only skills_) placeholders even if placeholderAPI is not running.
• Fixed not checking the max Lvl for masteries.
• Fixed where it always said "Loaded 0 language statements".
• Fixed skill activation getting called twice.
• Removed an old skill pyro from the config.
• Fixed config handler that in some cases it needed to use the default options when the config was not there.

API:

• Package namespace is renamed to org.skills, the whole API is incompatible with the previous one. Please update.
• PlayerInfo class is now SkilledPlayer.
  
• For any player related API usage, use SkillsAPI class.
• Added SkillEXPGainEvent requested by Kiricho for QuantumRPG plugin party system.
• setExp() can now be used as setExp(int exp, boolean silent) where if silent is true, it'll increase the level manually without calling levelUp method which calls SkillLevelUpEvent in SkilledPlayer class.
• Added getRawExp(), setRawExp(int exp) and willLevelUp(int exp) to SkilledPlayer class.
• levelUp calls SkillLevelUpEvent for each integer, and now it will continue calling these events if one of them is cancelled.
• Changed isHasValue from Sdsad class to hasValue.
• Added an API to add your own skills. Read below for more information. (Not complete)
  
• You can now set the added level for SkillLevelUpEvent event using setAddedLevel
• You can now directly access SkilledPlayer from events.
• All the events will now use Player, events will not fire for offline players.
• SkillActiveStateChangeEvent is now cancellable.
• In SkilledPlayer setters and getters for stats are no longer available directly. You have to use getStat(StatType) and setStat(StatType, int amount).
• SkillToggleDisableEvent is renamed to SkillToggleAbilityEvent. And since offline players can't toggle abilities, it now uses Player. Also getToggled is renamed to getAbility. setDisabled is also added. And it's no longer possible to setPlayer...
• In SkilledPlayer: isDisabled is renamed to isAbilityDisabled and toggleDisabled is renamed to toggleAbility. Always make sure to use these methods. Do not call SkillToggleAbilityEvent directly.
• The full wiki will be finished later.

And a lot more. I changed a lot of things that I completely forgot.