Refactored uniforms for better type safety
Refactored attributes for better type safety
Added WebGL_Custom_Attributes example
Fixed array of Texture and array of Matrix uniforms
Added Uniform.clone()
Use doubles for float uniforms
Cleanup WebGL_Custom_Attributes example
Merge pull request #59 from nelsonsilva/uniforms

Refactored shader uniforms and attributes for better type safety.
Added WebGL custom attributes examples.