alternate method for defining properties

I'm using backprop in my CoffeeScript classes so I needed an alternate method for creating properties. This is what I came up with. Usage from CS like so:

```coffeescript
class User extends Backbone.Model
  Backprop.create @, {
    name:     {coerce: String}
    username: {coerce: String}
    email:    {coerce: String}
    phone:    {coerce: String}
  }
```