Add flatstrap assets

Flatstrap version 1.75 from http://www.flatstrap.org/
Include flatstrap and its responsive version
Use success and danger buttons for answers

In order to get green buttons and red buttons, we'll just steal the
success and danger bootstrap button styles
Put footer on all pages
Sticky footer
Variable up the fixed footer
Pad the footer; style the answer
Admin page layout and copy
Style up the footer in super-understated way
Make all h1s centred
Sort out the home page a bit
Restyle wells
Give all h1s some top margin