Change this.transparent data structure from array to dict to match transgreedy mesher

Ref https://github.com/maxogden/voxel/issues/16
Revert "Change this.transparent data structure from array to dict to match transgreedy mesher"

This reverts commit 7963475bf0d49c9a8ddd789cd4d6fc8ea39f6046.
Add getTransparentVoxelTypes() for transgreedy mesher

Ref https://github.com/maxogden/voxel/issues/16