About page text, first pass.

Merges [30821] to the 4.1 branch.

props johnbillion, helen, markjaquith, nacin.
see #30435.

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git-svn-id: http://core.svn.wordpress.org/branches/4.1@30812 1a063a9b-81f0-0310-95a4-ce76da25c4cd