Fixed bug where menu does not toggle on click

fixes the error described here: https://github.com/Automattic/_s/issues/261
Merge pull request #262 from calvinwinter/master

_s: Update `.toggled` class to reflect revised `navigation.js` syntax. Fixes #261.
Remove WordPress.com-specific functions and definitions require line from functions.php; wpcom.php is now automatically included via plugin on WordPress.com.