Google Authorship: support apostrophe in author names

On the Sharing -> Settings page, if there is an apostrophe in the Google+ profile name (e.g. `Darrell O'Donnell`) the name will show with a `\` (`Darrell O\'Donnell`). This commit fixes it.

For more details, see original trac ticket:
http://plugins.trac.wordpress.org/ticket/2066