Admin signs in

And admin/videos#new
Admin adds a video (without cover)
Admin adds a video
Admin adds a video - CarrierWave S3 support
Fix "undefined method `scale`" error in heroku
Fix timeout problem in heroku
Add video_url (Watch video)
Feature test for adding video
Merge pull request #13 from ascendbruce/week6-part1

Week6 part1