ofxCrossfadeShader

how to use

	ofxCrossfadeShader::beginShader(imgTexRefA, imgTexRefB, pct);
			tex.draw(0, 0);
	ofxCrossfadeShader::endShader();
	
	or
	
	ofxCrossfadeShader hueShader;		
	ofxCrossfadeShader.begin(imgTexRefA, imgTexRefB, pct);
			tex.draw(0, 0);
	ofxCrossfadeShader.end();