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

support/aphlict/server/aphlict_server.js

@@ -242,7 +242,7 @@ http.createServer(function(request, response) {
         'version': 6
       };
 
-      response.writeHead(200, {'Content-Type': 'text/plain'});
+      response.writeHead(200, {'Content-Type': 'application/json'});
       response.write(JSON.stringify(status));
       response.end();
     });