added functionality plus additions from greenisus

[nathanfjohnson]

This fixes a problem with the animation duration not working unless 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