Update site design (from @gkoberger)

Close #61 with a design based on the mockup + PSD from @gkoberger.

I made some liberties with the conversion, and implemented what I thought
made sense for a responsive design.
Fix colours on background image
Bold the <h1>
Update version number
Improve desktop design and tablet-size designs
Improve brick texture bg
Finish mobile/tablet versions of index page
Remove hand unicode
Fix mobile bugs and docs bug
Add top-margin to .top links
Cleanup CSS
Fix grid issues reported by @sole
Use less intense brick image
Add newline to base.html
Add changes to templates instead of output
Add info on building/updating the Brick website
Merge pull request #151 from mozilla/new-coat-of-paint

@tofumatt rocks.