title: Chromecast send message returns invalid parameter error
body: <p>on my sender side after i successfully create a session I have:</p>
  
  <pre class="lang-js prettyprint-override"><code>var onRequestSessionSuccess = function(session) {
              var namespace = 'urn:x-cast:super.awesome.example';
  
              var message = 'It worked!';
              console.log('Session created.');
              session.sendMessage(namespace, message, onSuccess, onFailure);
  }
  </code></pre>
  
  <p>on the receiver side I have: </p>
  
  <pre><code>var namespace = 'urn:x-cast:super.awesome.example'; 
  
          var messageBus = castReceiverManager.getCastMessageBus(
              namespace,
              cast.receiver.CastMessageBus.MessageType.JSON
          );
  
          messageBus.onMessage = function(event) {
              var sender = event.senderId;
              var message = event.data;
              console.log('received message!');
          };
  </code></pre>
  
  <p>on the onFailure function on the sender app, I console.log the error message and
  whenever i run it i get :</p>
  
  <pre><code>Object {code: "invalid_parameter", description: "Invalid namespace", details: null}
  </code></pre>
  
  <p>how is 'urn:x-cast:super.awesome.example' an invalid namespace? It follows the convention of including 'urn:x-cast:' before the custom part. Also even when I replace the namespaces with something valid like: "google.cast" I get the following error message:</p>
  
  <pre><code>Object {code: "invalid_parameter", description: null, details: null}
  </code></pre>
  
  <p>what is the invalid parameter here?</p>