gitignore file
down arrow is hideable via .hideDownArrow
stop button square hideable via .hideStopSquare
set an fmaxf guard to keep lineWidth from going below 1 (help render problems when setting a small frame)
Adjusted the radius on the progress arc so that it doesn't have a hairline between it and the outer circle
Added a callback block for when the checkmark finishes animating off.
testing a smaller circle to see rendering tweaks, testing .hideStopSquare, .hideDownArrow, and testing the completion callback.