Added classes which help with asynchronous loading of drawables.
Allows a loading task to be associated with a View which will update the View's drawables when complete.
Added simple example of AsyncDrawables.
Fixed typo in BaseAsyncDrawableTask
Updating BaseAsyncDrawableTask to utilize ThreadingUtils.runOnUIThread so binding happens instantly if running on the UI thread.
Allowed early termination of BaseAsyncDrawableTasks during onBind().
Added comments to uncommented abstract methods.
Updated example to match above changes and some cleanup.
Added some more specifics to AsyncDrawableTask.bind JavaDoc
Added an example of AsyncDrawable implementation in a ListView that demonstrates safety through View recycles.