Failing specs for method double calls + little fix

* methods would not get renamed if we already respond to a renamed
  method name. If we then override that method and try to add a
  callback it won't work.
Make inheritance work as expected especially with super

  * only call the callbacks defined for a super class if super
    is really called
  * achieved by getting the class a callback is defined on into
    the method context - able to delete all of that lookup code
    I am super happy about this =)
  * see ff1dc46014f9 for details on which test cases where failing
    without this
remove superfluous module_eval + improve naming
Get rid off AfterDo::Instance since there is not much going on thee anymore

* all the thanks go to the simplified and improved lookup =D
Get rid off class module, everything goes on class now
_after_do_callbacks can now be private like I wanted it to be =)
Removed last eval call as they are not necessary on self ;-)
Code restructuring/renaming for readability
Actually we do not need the the accessor anymore at all - jay
Merge branch 'master' of github.com:PragTob/after_do