Twenty Thirteen: better styles for blockquote italic and bold text. Fixes #24471.

git-svn-id: http://core.svn.wordpress.org/trunk@24393 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Thirteen: use lowercase color hex value in RTL CSS file, props zeo. Fixes #24474.

git-svn-id: http://core.svn.wordpress.org/trunk@24394 1a063a9b-81f0-0310-95a4-ce76da25c4cd