Add Skins

This release allows npcs to have skins
NPCLib is usable as a plugin so you don't need to use maven
This changes npclib's package from techcable.minecraft.npclib to net.techcable.npclib

Initial Release

Support for spawning human npcs on 1.8, fake 1.8, 1.7.10, and 1.7.9
Support for non-human npcs with citizens