experimenting with branding.
Start to clean up the HTML and CSS to match the mocks.
add the persona watermark in the footer
Place the arrow as a background image on #signIn instead of having its own container. It makes the transition smoother.
Reset background color to something neutral.
First pass at backgroundColor support.
Fix jslint warnings reported by Travis.
Close the stupid string.
And remove unreachable return statement.
Styling cleanup. Add bg color inputs to example RP.

* Make sure colors look correct on mobile
* In desktop, add a box-shadow to the right hand side of the user area to match the arrow.
* Remove grain.png from the message screens. It's ugly with the new stylings.
* Add bg color and RP name inputs to example RP.
Extract validation and color derivation into separate functions.
Extended footer text on @ryanfeeley's suggestion.
Optimize new arrow, use through data: URI.
Optimize and inline new footer image.
Add unit tests for validateBackgroundColor.

* Fix an issue with the length check that would allow any length string > 3 as
 long as all characters were correct.
Add text color abstraction to help with testing.
Add tests for RPInfo.foregroundColor() function.
Add djc to the CONTRIBUTORS list.
Merge pull request #3589 from mozilla/branding

RP Branding!