added functionality plus additions from greenisus

This fixes a problem with the animation duration not working start progress is 0.
greenisus added a method for specifying the duration.
greenisus added a method for removing the stop button
I put a property in for specifying the progress line width
I put a boolean property in for turning on pie mode, making the progress line fill the circle.
I did Some refactoring and small bug fixing
Readme edited