Added Eclipse and IDEA gradle plugins and title-cased project name.
Reverted project name change for now.
Improved tree support and fixed lack of tree generation (fixes #101).
Fixed outer skin layers not appearing (fixes #162).
Fixed swords stopping digging in Survival mode (fixes #349).
Consider world created before WorldLoadEvent is called.
Added Eclipse project name override to build script.

Intended to fix weirdness with importing the files generated by the
Eclipse gradle plugin.
Added snow block placement handling.
Added note about Trello to CONTRIBUTING.md.
Refactored out use of JSONObject in the protocol in favor of TextMessage.
Minor cleanup.
Added API for displaying particle effects.

Particle effects can be played to individual players and players near a
location. The Particle enum defines the available particle effects.
Particles can be displayed in groups with a spread, and some particles
make use of a MaterialData or an extra data float, which defines speed or
some other property of the generated particles.