Add true index and groups page
*Add index page
*Point to index page
*Change root and galleries links accordingly
*Add Group object and files
*Add GroupMembership object and files
*Add /groups page
Add Groups pages and functionality
*Add new, edit pages and abilities
*Add form
*Add delete ability
*Add show page for groups
Add dependent: :destroy to group memberships
Add group membership capabilities
*Add button and ability to join group
*Add button and ability to leave group
*Automatically give membership to creator of new group
*Add list of members to groups show page
Refactor controllers
*Add add_member and remove_member methods
*Change links to @gallery, @group instead of _path