function compileShader()
	{
		var true_shader = new GL.Shader(true_vs, true_fs);
		for(var i in true_shader)
			shader[i] = true_shader[i];
		shader.ready = true;
	}
Create a shader from two urls. While the system is fetching the two urls, the shader contains a dummy shader that renders black.
@method Shader.fromURL
@param {String} vs_path the url to the vertex shader
@param {String} fs_path the url to the fragment shader
@param {Function} on_complete [Optional] a callback to call once the shader is ready.
@return {Shader}