Feature/without active support second try cleaner diff

@jnicklas 
The summary diff is the same, but I have spit up the commits, so one can follow each individual step. 

- Preventing it completely is impossible, since I want to reuse the whole spec with and without ActiveSupport, so moving it to an extra file seems unavoidable (and that messes up the end diff). 
- no vendoring for `.constantize`: yep, it works! (at least with ruby 2.1). I thought this method does not support name-spaced constants, but I was wrong. 

I did no change the spec (logically), only prepended all constants with `scope_const::`. Guess, you have to believe me on that, it's not that clear from the diff. 


Could we please get this pull-request in, you would only benefit from it, don't we all agree? 

With all the respect from Berlin, 
Roman