Updates to the About page:

* A live color scheme preview
* Replace the hard-coded version number
* Copy edits
* New screenshots
* Size adjustments to the header and WP badge
* Capitalize 'Open Sans'

See #26387, props markoheijnen, ryelle, siobhan, melchoyce.



git-svn-id: https://develop.svn.wordpress.org/trunk@26737 602fd350-edb4-49c9-b593-d223f7449a82