title: Backbone: navigation callback
body: <p><em><strong>What I have:</em></strong></p>
  
  <p>I navigate through backbone's views via <code>Backbone.history.navigate("someFragment", {trigger: true})</code> method</p>
  
  <p><em><strong>What I want:</em></strong></p>
  
  <p>I'm searching for correct way to pass navigation callback function. Means something like <code>Backbone.history.navigate("someFragment", {trigger: true}, callbackFunction)</code>. Important point - I want that callback proceeds ONLY ONCE, and when I call <code>Backbone.history.navigate("someFragment", {trigger: true})</code> next time, it won't be proceeded.</p>