ActiveRecord::Enum matcher

Hi guys,

I started a matcher for the  [ActiveRecord::Enum](http://edgeapi.rubyonrails.org/classes/ActiveRecord/Enum.html). I know we can`t merge this now since no released rails 4.1.0.

I only want to show you guys the idea =) and ask one thing: ActiveRecord::Enum is only on rails 4.1.0, how we can skip this specs in older rails versions?
I just realized... RecordWithArrayValue is divorced from the `record_with_array_values` method definition. What do you think about using `record_with_array_values.class` everywhere you use RecordWithArrayValue? (I'm just thinking, if this class name gets changed somehow, then you'd have to change this everywhere otherwise)