Adding Group and Membership models. see #27

- set up group to accept memberships and create a
  collection of memberships
- set up form to handle naming a group
Form proper groups JSON for API. see #27
more dynamic group save UI. #27
Showing list of groups and create voting_rights based on members

- checks to see if group users are already added
some cleanup of form escaping. see #27
separate out templates and views for different group collections. #27
cleanup. closes #27
Merge pull request #50 from cremalab/groups-27-rb

Groups