Add mp3 format to allow converting to mp3 files
Add test to convert to mp3
Log ffmpeg commands
Merge pull request #16 from tahajahangir/add-mp3-format

Add mp3 format to allow converting to mp3 files
Merge pull request #18 from tahajahangir/improve_logging

Log ffmpeg commands
Grab stream bitrate in MediaFormatInfo
Grab stream bitrate in MediaStreamInfo
Stream bitrate should be None when it's N/A on ffprobe output
Add tests for MediaStreamInfo.bitrate
Merge pull request #17 from tahajahangir/grab-stream-bitrate

Grab stream bitrate
Assert thumbnails exist after call to `thumbnails`
Merge pull request #19 from tahajahangir/multiple_thumbnails

Create multiple thumbnails in one ffmpeg call
Merge branch 'master' into develop