Highly recommended to update the plugin to 7.2.

Changelogs:
+ Removed configuration parts from NickAPI class and put it to NickConfig class
+ added a second respawn method for 1.8.8 in order to prevent problems
+ removed MineSkin library and using Apache HTTPClient5 to request data from the websites (Mojang/Mineskin API usw..) File size decreased from 4MB to ~ 2MB.
* fixed an issue for players not getting nicked
* prevent a bug that cracked players getting kicked while unnicked (Use NickConfig.setCracked( true ) to fix it )

Please use for Maven the version 7.2-SNAPSHOT - Older versions may be removed due to API changes & bugs