Add H264 Caption extraction
Extends timeout for caption extraction.

This is probably not the best way to handle this.. The problem is if the
recording file stops growing for a few seconds we time out. This allows
you to extend the timeout with the --endtime parameter and by default
sets the endtime to 1 hour after a recording started (if it is using
mythtv naming conventions.)
Merge pull request #17 from rkrishna1/fixes/0.27

Fixes/0.27