(DNM) Fix bug 936452: Add static maintenance page

The only intention here is to keep these files under revision control.
Getting them served up will always require additional work.

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A few notes:

* This assumes the CDN will be available during maintenance. We are still [looking into this](https://bugzilla.mozilla.org/show_bug.cgi?id=935002#c14), so please don't merge until CDN access is confirmed. Feel free to review at any time, however.
* The code duplication here really kills me (especially the Google Analytics stuff) but it is a static page. Thoughts on refactoring Google Analytics or somehow automating the creation of this page--including whether it would be worth the effort--are more than welcome.
* I tried to keep the page as [simple](http://www.usabilitypost.com/2010/02/07/the-laws-of-simplicity/) possible, so I left the TumblBeasts out. I can add them in if anyone feels strongly about it.
* Not doing any `?build=hash` CDN cache busting here given the manual work involved, but I'm open to working them in if we feel we need them.