Add .checkstyle to .gitignore
Add VoxelVolume super-implementation for World and Chunk; moved methods from World and Chunk. Add EntityUniverse super-implementation with methods to get Entities
Add Vector3i block and voxel getters to VoxelVolume
Merge pull request #46 from killjoy1221/gitignore

Add .checkstyle to .gitignore
Updating Block event with reference to Voxel

Updated `BlockEvent` with `Voxel getVoxel()` for block/position. I'm debating
renaming the events to `VoxelEvent` but that may be too different from
what devs are accustomed to.