* Fix#117 - Add ability to specify alternative text for media attachments
- POST /api/v1/media accepts `description` straight away
- PUT /api/v1/media/:id to update `description` (only for unattached ones)
- Serialized as `name` of Document object in ActivityPub
- Uploads form adjusted for better performance and description input
* Add tests
* Change undo button blend mode to difference
* Fixes#1985
- add migration AddMediaAttachmentMeta, which add meta field to media_attachments
- before saving attachment, set file meta if needed
- add meta in api
* add spec
* align the “size” format for image and video
* fix code climate
* fixes media_attachment_spec.rb
* Fix#2108 - Fix gif uploads
Add specs for media attachment gifv conversion
* Add ffmpeg to travis
* Make travis install ffmpeg, not libav
* Switch travis to trusty
