Use HTTPRL's non blocking request inside of _amon_request()

Inside of _amon_request, drupal_http_request() is used. This can be sped up by using the HTTP Parallel Request Library to issue a non blocking request. What this means is it will not wait for the response back from Amon, preventing Amon from causing too big of a performance impact due to network traffic on the local box.

  httprl_request($url, array(
    'headers' => array(
      'Content-Type' => 'application/json',
    ),
    'method' => 'POST',
    'data' => json_encode($data),
    'blocking' => FALSE,
  ));
  $result = httprl_send_request();