This plugin disables posting for accounts that do not have a
validated email address.

Example:

  addPlugin('RequireValidatedEmail');

If you don't want to apply the validationr equirement to existing
accounts, you can specify a cutoff date to grandfather in users
registered prior to that timestamp.

  addPlugin('RequireValidatedEmail',
            array('grandfatherCutoff' => 'Dec 7, 2009');

You can also exclude the validation checks from OpenID accounts
connected to a trusted provider, by providing a list of regular
expressions to match their provider URLs.

For example, to trust WikiHow and Wikipedia users:

  addPlugin('RequireValidatedEmailPlugin', array(
     'trustedOpenIDs' => array(
         '!^http://\w+\.wikihow\.com/!',
         '!^http://\w+\.wikipedia\.org/!',
     ),
  ));

Todo:
* add a more visible indicator that validation is still outstanding
* test with XMPP, API posting
