title: Emberjs: Prevent back button from moving into another state
body: <p>When a state describes a view rendered in a modal/popup, we ideally want the user to only navigate away from it through offered options i.e Save or Cancel buttons. </p>
  
  <p>The back button presents a real issue when you design your application with states in mind and you use modals to render views in certain states (New, Edit ...). </p>
  
  <p>Is there a way to hack into the states history to prevent, when desired, landing in a state through the back button.</p>