Hygiene: Don't use content_wrapper

Use h1, .content h1 or #firstHeading instead.
We should really get out of habit of using ids for
styling. (http://screwlewse.com/2010/07/dont-use-id-selectors-in-css/)

(Note this also fixes the style guide)

Change-Id: Ib14cdf4fe8092f50e69bf06e7e25f3747f85c945
Merge "Hygiene: Don't use content_wrapper"