Reformat source code with IntelliJ IDEA preset

Some of this may be slightly off but it's better than it was
Merge pull request #152 from Kobata/style-reformat

Reformat source code with IntelliJ IDEA preset
Update README.md, add CONTRIBUTING.md

Signed-off-by: Steven Downer <grinch@outlook.com>
Add modifed google style checkstyle.xml

Commented-out things are features that require unreleased versions
of checkstyle.
Github's urls are case-sensitive
Fix documentation of PluginManager.getPlugin

It is looking up by ID, not name
Update to new formatting and complete incomplete JavaDocs.
Remove some methods in TextMessage in favor of MessageBuilder

Signed-off-by: Matthew Messinger <mattmess1221@gmail.com>
Merge branch 'master' of git://github.com/SpongePowered/SpongeAPI into chat

Conflicts:
	src/main/java/org/spongepowered/api/Game.java