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
Updated production Dockerfile and specified the proper host information for production database.
Update User#parse_subscriptions to use new schema

Pulled external API logic out of the user model
Fix merge conflicts
Modified ember gitignore file to ignore production builds
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