Added proxy support (fixes #114). Thanks @Johni0702!

Proxies such as BungeeCord have the option to forward the real address,
UUID, and properties from the auth process to the backing server so that
they can appear to be in online mode even if they are not.
Minor style fixes.
Fixed support for 1.8's string-based item ids.
Convert data types during server.properties migration (fixes #392).
Added player visibility API (closes #121).

Players are hidden fron another player's tab list and entity updates.
Also renamed other canSee methods to canSeeChunk and canSeeEntity.
Removed TextWrapper in favor of the client word-wrapping.

Formatting is still a little awkward. When new-style formatting is added
the old-style formatting can be properly converted, fixing any weirdness.
Merge pull request #1 from GlowstoneMC/master

Merge updates