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?
Avoid using {...} for multi-line blocks.