Handle session timeouts within ajax calls nicely.

index.js

$httpProvider.responseInterceptors.push(function($window){
  return function(promise){
    return promise.then(function(){
      // session is valid, carry along...
      return promise;
    }, function(error){
      if (error.status == 401) {
        // invalid session, need to re-login...
        $window.location = '/login';
      }
    });
  };
});