Allow modifying playback speed

[BinaryMuse]

Depends on BinaryMuse/timex#1

[orientalperil]

@BinaryMuse This request has come up again. Can you help me understand what changes I'll need to make to get this to work?

[BinaryMuse]

@hekevintran I just pushed Timex v1.1.0 which should enable variable timer rates in Timex (see BinaryMuse/timex#2). At a high-level, Kinteophone just needs to provide a public API to call setRate and getRate on the underlying timer. However, if you're using Kinetophone for audio/video playback (as you are), you'll also need to make sure to query the current rate and use it to modify the <audio> tag's playback rate, etc.