Changed seconds to milliseconds internally (though the API remains the same).
Renamed getInBetweenValue() to getBoundedValue(). Got rid of commented out code. Got rid of the behavior where togglePause() was not identical in behavior to play/pause. Added new unit tests.
Added support for loading animated gifs. Note that not all animated gifs will properly load. (There seem to be some limitations with Pygame and the PIL/Pillow module that prevent all GIFs from loading correctly.)