Accessibility Fixes

A bunch of accessibility fixes. Will need someone to double check and to
fix styling as there were instances where I had to change headings (from
H2 to H1 etc.) so they probably don't have the right styles anymore.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	webcompat/templates/thanks.html
Another Tab -> Space

Missed One.
Merge branch 'master' of github.com:andrewmcgivery/webcompat.com into andrewmcgivery-master

* 'master' of github.com:andrewmcgivery/webcompat.com:
  Another Tab -> Space
  Accessibility Fixes