Added a new config option (night-speed-curve) which lets you tweak how the percentage of players sleeping affects the night speed. Please refer to the config section on the overview page for information about how this works and for a visual reference. The default value should mimic the old style. Thanks to _theminerdude_ aka Drathares @ NarniaMC for helping with this formula!
Fixed a bug that may have been around for a while: new options added to the config didn't insert the proper default value into older configs.
Updated the pom.xml to build against Bukkit 1.13.1