fix(authenticate): return for error catching

```javascript
auth.authenticate(profile, token).catch(function() {
  LoginModal();
});
```
When auth0 is trying to get the token/profile and the user doesn't exist anymore you get an error. The problem is that you can't hook into that error to redirect them etc

here is an example of what I'm using 
```javascript
.run(function(LoginModal, auth, store, jwtHelper, prefix) {

  function checkAuth() {
    if (!auth.isAuthenticated) {
      var token = auth.idToken || store.get(prefix+'token');
      if (token) {
        if (!jwtHelper.isTokenExpired(token)) {
          auth.authenticate(auth.profile || store.get(prefix+'profile'), token)['catch'](function() {
            LoginModal();
          });
        } else {
          var refreshToken = auth.refreshToken || store.get(prefix+'refreshToken');
          // Either show Login page or use the refresh token to get a new idToken
          if (refreshToken) {
            auth.refreshIdToken(refreshToken).then(function(idToken) {
              store.set(prefix+'token', idToken);
              auth.authenticate(auth.profile || store.get(prefix+'profile'), idToken);
            })['catch'](function() {
              LoginModal();
            });
          } else {
            LoginModal();
          }
        }
      } else {
        LoginModal();
      }
    }
  }
  $rootScope.$on('$locationChangeStart', checkAuth);
  checkAuth();

});
```


another way to get the error is hooking into the profilePromise error
```javascript
.config(function($httpProvider, authProvider, jwtInterceptorProvider) {
  authProvider.init({
    domain: 'sometimeawesome.auth0.com',
    clientID: 'something-secret',
    callbackURL: window.location.href
  });

  // @ngInject
  function initRealtime(Auth, profilePromise) {
    profilePromise.then(function(profile) {
      console.time('init services');

      return profile;
    })['catch'](function(err) {
      console.error('redirect etc', err);
      LoginModal();
    });
  }

  authProvider.on('loginSuccess', initRealtime);
  authProvider.on('authenticated', initRealtime);
});
```