Increase atlas size to 2048x2048 from 512x512

According to http://webglstats.com/#h_texsize, 100% of WebGL users
in the wild support up to 2048x2048 textures. With 4x4 repeated/padded
textures 16x16 each, this will support up to 1024 textures per atlas.
Restore support for voxel-texture 0.5.6

Revert "Use more compatible texture API"

This reverts commit 58967dba81734134f1ad8d52b18d7203eafc27c3.

Conflicts:
	index.js
Add support for multiple texture modules
Revert "Increase atlas size to 2048x2048 from 512x512"

This reverts commit a8ef28f7c2645dc106737bbae556e816d2409fbe.

Moved to deathcap/voxel-texture-shader@73806ef3eee719d7a27509a57d516899f7706dd4
Update to voxel-texture 0.5.8
Merge branch 'master' of github.com:deathcap/voxel-engine

Conflicts:
	index.js

Ref https://github.com/deathcap/voxel-engine/pull/1