Don't use superclass

Instead, move attribute reader logic to separate method.
If you want to override a reader you can do it like this:

````
def my_attribute
  original_attribute = read_attribute(:my_attribute)
  …
end
```
Merge remote-tracking branch 'refs/remotes/origin/jens-version'

Conflicts:
	spec/attribrutal_spec.rb
Made specs pass.