Add players for Recording detail page #30

As well as the player for entire recording, include players for thesplit speeches.

Note that this doesn't include the conversion tasks.
Convert uploaded audio to .mp3 for benefit of player #30
Do partial mp3s with 'copy' pseudocodec #30

(For less lossiness, and faster conversion, we only transcode
to mp3 once, and then split the partial mp3s out with
-acodec copy)
Tests for #30 with non-mp3 upload
Some notes on testing API

these came in useful while developing against #30
Remove unneeded js #30

(as per Matthew's comment, speeches.js already instantiates mediaplayer
is audio-small isn't provided)
Merge branch 'whole-recording-features'