Sponsorship functionality & UI

PT story https://www.pivotaltracker.com/story/show/78039462

- Add functionality to link sponsor & orphan (i.e. create sponsorship)
- Sponsored orphans shown on sponsor's page
- Sponsorships can be ended by clicking link next to orphan's name on sponsor page
- Establishing a sponsorship marks orphan as 'Sponsored'
- Only Active Unsponsored orphans displayed when creating new sponsorship link
- Only one sponsorship relationship can be established between a sponsor and orphan (enforced in db)

UI is not final as client has sent new specifications
http://osra-nga.herokuapp.com/admin/sponsors/2/sponsorships/2 is the url for the delete
This reads to me sponsor.id 2, sponsorship.id 2.
can't we just find on sponsorship.id and delete rather than building up the sponsorship from orphans and sponsors?