title: Mongoose createConnection promise
body: <p>Is there some way I could return a promise from <code>createConnection</code>, so I don't have to use listeners</p>
  
  <p>I'm using Bluebird for promises.</p>
  
  <p>I'd like to use <code>.then()</code> and <code>.catch()</code> instead of listeners <code>.on('error', callback)</code> and <code>.on('open', callback)</code></p>
  
  <p>This is how I initialise the connection</p>
  
  <pre><code>_initConnection(connectionSettings){
      Mongoose.Promise = Bluebird;
      this.connection = Mongoose.createConnection(connectionSettings);
  }
  </code></pre>