created requested_sponsor_count field in active admin views

part of PT story https://www.pivotaltracker.com/story/show/79157380
(while testing jira this relates to OSRA-83 subtask OSRA-85 #resolved
field shown in
- show
- create
- update
Merge pull request #3 from PurityControl/requested_orphan_count

created requested_sponsor_count field in active admin views