Implement OrganizerHelpers, Interpipe::Organizer and Pipe + Splitter as its subclasses

Re #26 

I love the amount of deleted code here, but OrganizerHelpers is not yet tested. The biggest change from the original spec is use of `organizers=` class setter instead of implementation-specific `#pipe` and `#split`.
What do ya think, @flexik?
Unused method argument - `options`. If it's necessary, use `_` or `_options` as an argument name to indicate that it won't be used. You can also write as `perform(*)` if you want the method to accept any arguments but don't care about them.