Developers banner and popup (bug 1052880)

https://bugzilla.mozilla.org/show_bug.cgi?id=1052880

FxA migration banners on devhub.


![fx-migration-desktop mov](https://cloud.githubusercontent.com/assets/211578/4412923/5044356c-44fe-11e4-8378-f7a5c9bdf695.gif)

I had copied it over to a repo called `marketplace-elements` and did a `bower install ../marketplace-elements`. I wasn't sure how the packaging with bower was coming along or how to get it to work correctly so I just copied it from there. Maybe zamboni can serve the `bower_components` folder and concatenation will solve our problems?

I'm thinking I'll push up the marketplace-elements repo and get fireplace and zamboni both pulling from it at a later date.