Document options passing in ES7 property decorators

[jwahyoung]

In the Custom Attribute documentation, it's mentioned that you can pass options to @bindable in the ES6 class decorators, like so:

@bindable({
  name:'myProperty', //name of the property on the class
  attribute:'my-property', //name of the attribute in HTML
  changeHandler:'myPropertyChanged', //name of the method to invoke when the property changes
  defaultBindingMode: bindingMode.oneWay, //default binding mode used with the .bind command
  defaultValue: undefined //default value of the property, if not bound or set in HTML
})

The ES7 property decorators negate the need for the name property, but it's not explicitly stated that you can do this, which seems to work:

@bindable({ attribute:'my-property', changeHandler:'myPropertyChanged', defaultBindingMode: bindingMode.oneWay, defaultValue: undefined }) name;

It might be worthwhile to add an explicit example of this.

[EisenbergEffect]

Made a note of it here: #181