Properly used the AsyncTask to no longer freeze the UI thread by
blocking on the get() call.  Used a callback interface to process the
resulting mp4 url and then start an intent.
Changed progress bar to a horizontal bar to show total progress.
Added back button handling to cancel the current task.

Added handling of orientation changes so that another task isn't started
when one is already running.

Increased minimum supported API level to 5 so I can capture back buttons
to cancel the task.