Create a way to flag status of sheep. Want it to specify how the animal left the farm. Include method of filtering sheep on Shepherd's show page.

[pschloss]

• [x] Need to capture the date that the animal was deactivated
• [x] On an animal's edit page, have a selector to indicate whether the animal is currently active or was stillborn, sold, culled, died
• [x] Need a way to denote that an animal has been deactivated (add to header?)
• [x] Incorporate integration tests