* feat(server): Support webm without transcoding.
Transcoding result doesn't appear to be used by anything expect for quicktime.
* feat(server): Fix the asset uploader for .avi
It needs to be transcoded.
* feat(server): Most browsers doesn't support avi so use mp4.
* feat(server): Address PR comments
* Addressed the PR comments
I moved the function that checks the mimetype to a central location in asset-utils and made tests for it.
* Rollbacked to the way transcoder was decising things to transcode.
