Add settle button to user page: check
Change logout button to icon
User group models, migrations, associations
Migration: add group ID to bills
Add group association and splitting methods
Add bills association
Add Bill#in_group?
Refactor #randomized_split_amounts
Generate api/user_groups controller
Add :user_ids as attr_accessible
Initial api user group actions
Add API/UserGroups routes
Fix namespacing
Add #index action
Add necessary foreign_key to bills association
Add bills to #show and #index rendering
Bootstrap groups JSON
Process bootstrapped group data
Add groups panel view and template
Render groups panel