Fix the background job of sending email after a user subscribes to a repo

- Inside resque_def, we have to use repo_sub instead of self to refer
  to repo_subscription
- In adding_repos_test, user must sign in otherwise user_id for
  repo_subscription is nil
Don't login in adding_a_repo test

- It uses mockstar credentials which don't work when request is made
  to Github to get current user's repos from Line 14 of ReposController
Use existing repo because GithubBub complains it can't find codetriage2
Merge pull request #191 from prathamesh-sonpatki/fix_background_send_triage

Fix the background job of sending email after a user subscribes to a repo