Added a contour for the rim on the progress wheel

Added contourColor and contourSize to the attr to allow for a border to be drawn around the rim of the ProgressWheel: see attached imge
![screenshot_progresswheels](https://f.cloud.github.com/assets/1560762/1791121/5a4182ac-6987-11e3-8d72-8ec36867a5fe.png)