R1:44198d68a769

Use the correct `Content-Type` for the Aphlict status route

Summary: The `/status/` route for the Aphlict server returns JSON.

Test Plan:
```lang=bash
> curl -I http://127.0.0.1:22281/status/
HTTP/1.1 200 OK
Content-Type: application/json
Date: Fri, 02 Jan 2015 13:08:34 GMT
Connection: keep-alive
```

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11144