Only convert one column for now, and show time took
More testing tweaks
Move absolute coordinate calculation out of loops
Pretranslate block IDs

No noticeable speed-up
Avoid array construction, about 30index.coffee performance improvement
Inline voxelIndexFromCoordinates
Fix only converting one layer
Fix default block ID translation
Convert all chunks
Run zlib chunk decompression in a web worker. Ref GH-1

Could be much improved. Buffer conversions in browserify
is tricky.. web workers can only transfer ArrayBuffers, which can
be viewed through typed arrays (Uint8Array), but NodeJS has its own
Buffer type, and native-buffer-browserify implements Buffer as a
Uint8Array in Browserify 3... but ArrayBuffers have no 'length' (though
they do have a byteLength) , so they have to be casted to Uint8Array,
except zlib and node-minecraft- protocol needs Buffers. Its all
very confusing. This webworkified zlib decompression now finally
works, but it is only 40% of the bottleneck, the other is the chunk
conversion (about 30% CPU time).