mtUpdateSignInWidget = function (u) {
    if (u) {
            // u is undef coming in
    } else {
        // mtGetUser returns an object when run from the console

<?xml version='1.0'?>
<XRD xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'>
        <Subject>acct:steveivy@gmail.com</Subject>
        <Alias>http://www.google.com/profiles/steveivy</Alias>
        <Link rel='http://portablecontacts.net/spec/1.0' href='http://www-opensocial.googleusercontent.com/api/people/'/>

"""
URI template handling:

Sample code for how to take a URI Template and turn it into the webhook call to send the activity consumer the activity stream location.