Add ability to speed up and pitch shift downloaded audio books

[pgray007]

It would be great to offer the option to speed up, in 0.1X increments up to 2.0X, downloaded audio books, ideally applying a pitch shift to avoid the faster audio sounding higher-pitched.

This would be helpful for players that don't have this feature, like the Garmin series of fitness watches, and provide a dramatic savings for some of the epic 50+ hour audiobooks that I like to tackle during long runs.