Minor code changes
Add more exposition to the README
Merge remote-tracking branch 'evancz/master'

Conflicts:
	README.md
Crate: split out cube
README.md: add 'Coding with Shadertoy' setion
Move shaders to Shaders/
Refactor Main, Display
Add SimplePlasma
README.md: add Importing section
Add Voronoi Distances shader
Add Fire shader
Use all 3 simple shaders in cubes demo
README.md: link to issues
README.md: fix issue links
README.md: add purpose, significance
README: add Credits section
README.md: cleanup
Merge branch 'master' into gh-pages
Update build/Main.js