Added shoulda-matchers
Updated active_model_serializers to 0.8.1
Changed relation of streams and channels

A stream should belong to a channel, and a channel have many streams.
Deleted the HABTM table.
[Closes #18]
Merge branch 'master' into stream-belongs-to-one-channel

* master:
  Added specification for handling tags
  Added API to assign stream to channel
  Updated channels API
Merge from master
Merge branch 'master' into stream-belongs-to-one-channel

* master:
  Add thumbnail to the stream POST
Merge branch 'stream-belongs-to-one-channel'

* stream-belongs-to-one-channel:
  Changed relation of streams and channels
  Updated active_model_serializers to 0.8.1
  Added shoulda-matchers

Conflicts:
	app/models/stream.rb
	app/serializers/stream_serializer.rb