title: ui-router: open modal on $stateChangeEvent
body: <p>Some states in my app require further authentication. Eg a Edit state should prompt the user to enter a one time password.</p>
  
  <p>I would be nice to solve this horizontally: attach metadata to the states requiring extra auth (ie state.requiresExtraAuth: true), and plug some modal logic on the state change events. NOTE: What I am after is that the state does indeed load and the user can see it, but a modal forbids the user from continuing without entering the password. </p>
  
  <p>I tried adding a 'onEnter' property to the toState object param I get in the event listener function, but it didn't work :).</p>
  
  <p>Is something like that possible/how would you go about designing this use case?</p>