Implemented artifact upload with travis.

Signed-off-by: William Lebel <lebelwilliam@gmail.com>
Added remapper plugin for Bukkit backwards compatibility.
Switched to building against Glowkit.
Fixed Travis publication.
Made logger use more uniform (fixes #255).
Fixed disconnect when sending empty chunks.
Changed sound radius to be min(volume * 16, 16).
Added block placement handling for ladders and vines (see #119).
Added CONTRIBUTING.md (thanks @JeromSar).