Write out audio metadata frequently. Fixes #169.
If the source was switched among variant playlists that have different audio sampling rates and the initial audio metadata tag skipped, audio would dissapear. Instead, emit an audio meta tag at least once per second so that the decoder can get back on track after a change. Fix typo that caused audio DTS not to be written out properly.
Merge pull request #171 from videojs/hotfix/more-audio-meta

Write out audio metadata frequently. Fixes #169.