Single-bitrate playback

Reorganize the manifest-management parts of the plugin and swap to a regex based parser. This PR includes a bunch of additional testing infrastructure that hasn't made it into mainline yet. Instructions on using the plugin are now up-to-date in the README. Only "media playlists" (i.e. M3U8s that point directly to segment files) are currently supported. The buffer management algorithm is also very simplistic: a new segment is downloaded whenever the current buffered range endpoint is within five seconds of the playhead position.

An update to the video.js SWF to fix the buffered property is required to get this working correctly. I will update with a reference to the PR as soon as I open it.

@heff, @bclwhitaker, @gkatsev, @bcjwhisenant