Implement HTTP response messages

Summary: Fixes T7486. Implement HTTP response messages such as 200 OK and 404 Not Found. The status codes were taken from http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.

Test Plan: Navigated to /foo and saw the response showing 404 Not Found in the Network tab of Chrome.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7486

Differential Revision: https://secure.phabricator.com/D12299