Twenty Twelve: fix regression introduced in r23572, allow hide/show of Header Text in Customizer. Fixes #23600.

Also remove another `!important` -- and there was much rejoicing.

Props SergeyBiryukov and obenland.

git-svn-id: http://core.svn.wordpress.org/trunk@23711 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove unused variables. props GaryJ. fixes #23789.

git-svn-id: http://core.svn.wordpress.org/trunk@23712 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Twelve: load our special Google Font in the visual editor to improve user experience. Props to the Konstanthemes: kovshenin and obenland.

Closes #22499. See also r23672.

git-svn-id: http://core.svn.wordpress.org/trunk@23713 1a063a9b-81f0-0310-95a4-ce76da25c4cd