Formatting changes to accomodate respec.

Changed sections to divs around our requirements.
Changed requirements from H4 to div with class of requirement.
Merge branch 'halindrome-p-div'

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Merge branch 'master' of https://github.com/w3c/pfwg

Conflicts:
	media-accessibility-reqs/index.html
Merge branch 'master' of https://github.com/w3c/pfwg

Conflicts:
	media-accessibility-reqs/index.html