added ability to add features


I copied over the functionality started in this pull request: https://github.com/jrallison/rollout_ui/pull/5 since I couldn't pull that code
tests passing with rollout 2.0.0c
feature uses the new rollout interface to update groups & users
Merge branch 'updated_rollout_version' into add_feature

* updated_rollout_version:
  feature uses the new rollout interface to update groups & users
  tests passing with rollout 2.0.0c
fixed placeholder for the add feature
Merge pull request #1 from sleparc/add_feature

added ability to add features