Registration

An attempt to resolve https://github.com/WeAreTech/wearetech.io/issues/8
Move all this business logic into the `entities/city-application.ent.js` file. Use a signature with a single parameter like so:

```js
var cityAppEnt = CityApplicationEnt.getInstance();

cityAppEnt.registerNewCity(req.body)
  .then(function(res) {
      /**
       * Pass the City Document to Register Controller
       */
      req.flash('cityApp', cityApplication._id);

      res.render('preview', {
        cities: cities,
        cityApplicationId: cityApplication._id
      });
    
  });
```