use https to prevent 301s from Hipchat

Hipchat recently began returning 301s when a request is made without https. 

I haven't been able to find any reference to the change in Hipchat's docs, but we're consistently seeing it in production. The http responses look like:

```
{:status 301,
 :trace-redirects ["http://api.hipchat.com/v1/rooms/message"],
 :headers
 {"server" "nginx",
  "content-type" "text/html",
  "date" "Tue, 11 Feb 2014 01:38:34 GMT",
  "cache-control" "no-cache=\"set-cookie\"",
  "location"
  "https://api.hipchat.com/v1/rooms/message?format=json&auth_token=REDACTED&room_id=Development&from=Daniel&notify=1&color=yellow&message_format=html&message=hi",
  "content-length" "178",
  "connection" "Close"},
 :request-time 194,
 :body
 "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n"}
```