Move contribution guidelines to Docs and fix checkstyle
Fixes #91.
Add all hanging entities
Merge pull request #92 from AIOOB/hanging-entities

Add all hanging entities
Implement Rotations
Merge pull request #93 from Aaron1011/rotation

Implement Rotations
Implemented remaining entity type methods in GameRegistry.

* Updated API.
* Minor fixes.
Add villager implementation. Merges PR #95
Add WorldBorder implementation. Merges #89
Implement PrimedTNT. Merges #96
Implement ExperienceOrb. Merges #97
Return immutable lists in registry where applicable.

* Removed unneeded blank lines in MixinEntityPlayerExample.
Implemented the extended particles api.
Check for extra data before creating packets.
The default material type should be air.
Remove the 'with' prefix from the builder methods.
Removed the IllegalStateExceptions.
Added the field access.
Merge branch 'feature/particles' of https://github.com/Cybermaxke/Sponge into feature/particles

Conflicts:
	src/main/java/org/spongepowered/mod/registry/SpongeGameRegistry.java

Implemented the extended particles api.