Merge branch 'zencoder' into 'master'

Zencoder

This MR adds integration with the Zencoder API. It uses delayed jobs to schedule videos for encoding. A new `EncondedContent` model was created to store the data of Zencoder's notifications.

For testing, we are using the `zencoder_fetcher` gem to retrieve and post notifications on our callback url.

See merge request !18
3 jobs for master in 10 minutes and 30 seconds
Status Job ID Name Coverage
  Test
passed #2166594
cucumber

00:04:32

passed #2166593
rspec

00:03:08

passed #2166595
teaspoon

00:02:50