Fix an issue where unexpected debugging output would run afoul of automatic compression

Summary:
If you put "echo" or "print" statements into the code at random places (as I frequently do during development), they would emit before we enabled compression.

This would confuse the compression mechanism and browser. I tried using headers_sent() to selectively disable compression but that didn't appear to fix this interaction (I think emitting this text does not cause headers to send, but does let contet escape into some buffer which the compressor can not access).

Instead, push the header down a little bit so it renders after we activate compression.

Also make it slightly fancier / more hideous. WOW.

Test Plan:

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17052