Adds support for 1.13.
Adds auto-completion to command so you are able to see what skins are available and String[] getAvailableSkins() method to the SkinChanger class.
Reset skins now show to new players. Skin name inputted with command is now case sensitive.
Now the geometry name has to be geometry.my.custom.skin
skinchanger.use skinchanger.reset or skinchanger.*
