Adds user.registration.test entry

Fixes #1 

The start of the "heartbeat" automated monitoring transactions. 

This pull request will create test transactionals with the following payload:
```
$param = array(
  'activity' => 'user_register',
  'email' => 'dlee+messagebroker-heartbeat-test-user-register-' . rand(1, 99) . '@dosomething.org',
  'uid' => '666',
  'birthdate' => mktime(0, 0, 0, 6, 13, 1999), // 13 June 1999 (over 13)
  'merge_vars' => array(
    'FNAME' => 'Heartbeat-First-Name',
  ),
  'activity_timestamp' => <some timestamp>,
  'application_id' => 0
);
```
The `$config['routingKey'] = 'user.registration.test';` should result in:
- An email sent to `$param = array('email')`
- A record in the user db with the drupal_uid of "999".