Added RichMarkerView

In order to set up the HTML content, I'm currently doing this:

````
  initialize: function () {
    this.$el = $("<div>Hello</div>")
    this.overlayOptions.content = this.$el[0];
  }
````

However, you should be able to provide a template and the $el should get
set up automatically. So this isn't ready for the real world.