Correct media keys not being re-enabled after disable.

Updated SPMediaKeyTap to match what is in the main repo.

This update required the addition of two files.
Rational:  I had numerous cases where Hermes never regained the media keys.  I found a sure-fire way to reproduce this:
Launch Hermes and let it play.  Confirm the media keys work.
Launch QuickTime Player and play something.  Confirm the media keys are controlling QuickTime Player.
Quit QuickTime Player.
The media keys now launch iTunes.
Bring Hermes to the foreground
The media keys still launch iTunes.

With the changes in this pull request, when Hermes is brought to the foreground, it regains control through the media keys.