GLSL syntax error in WebGL.

After a lot of head scratching why I was getting syntax errors inside the GLSL implementation on webgl, I finally found that the version used in the shadertoy example and in the repository do not match. And the one in the repository does not work with webgl. I don't know if this is intentional or not, but at least it could use a note that the version in the shadertoy can be used in webgl.