Fix Bug 1083481 -  <details> fallback JavaScript and CSS is not #a11y

Existing code was good but was throwing an error. Updated test for Opera to be stand alone and not rely on something we probably removed.

Added ARIA roles.

Tweaked CSS.
Merge branch 'bug-1083481-details' of https://github.com/stephaniehobson/kuma into bug-1083481-details-again
bug 1083481 - wiki-edit cleanup with regard to details tag
bug 1083481 - Fix alignment of comments
Merge pull request #2924 from darkwing/bug-1083481-details-again

Fix Bug 1083481 - <details> fallback JavaScript and CSS is not #a11y