Revolute Joint

[neilmendoza]

I've added in ofxBox2dRevoluteJoint. I'm guessing from the fact that there's a jointType member in ofxBox2dJoint that you had intended that class to encapsulate all joints but seemed to make more sense as a separate class. Maybe ofxBox2dJoint could be renamed to ofxBox2dDistanceJoint with a typedef of ofxBox2dJoint for backwards compatibility. Also, haven't added an example but could do if you want...