Add YoutubeSubscription to the database

Get rid of tracked_subscriptions, now tracking is done with a boolean
column.
Delete user_controllers_spec.rb
Serve json from youtube subs controller
Update activities and users controller
Update User#add_tracked_subscriptions to use new schema
Ember is recieving json from rails api for youtube subscriptions
Update SessionsController
Fix merge conflicts
fix bug, file wasn't added
Merge branch 'master' of https://github.com/tyrbo/tunefish into sub_modal
Update User#parse_subscriptions to use new schema

Pulled external API logic out of the user model
Fix merge conflicts
Add specs for YoutubeSubscription
WIP calling YoutubeAPIWorker from sessions controller
Merge remote-tracking branch 'upstream/master' into youtube-subs
Merge branch 'youtube-subs' of https://github.com/wfro/tunefish into sub_modal
ember is talking to rails for subscriptions
youtube subscriptions show up in youtube modal
subscriptions have a tracked or untracked status in ember
ember updates rails models when changed