Updated to work with latest ofxMSAInteractiveObject

I only had to change two lines to get this to work with the ofx .84 and the latest ofxMSAInteractiveObject:

- line 15 : ofxMSAInteractiveObject::setPos(x, y); --> ofRectangle::setPosition(x, y);
- line 54 : isMouseDown() --> isMousePressed()

Sorry about the changes to the formatting (but honestly I think GitHub is displaying it weird).  This is tested and working.