Posible bugs
============
When getting parent and child in post_process, use 'parent' and 'child' ids in
the edge, not in the function args. Check all transformers.

Architecture changes
====================
- Consider using MULTIDIGRAPHs (would have to change _all_ edge accesses)
- Improve linearizer arch
  - make a common base to extract and a ?navigator/expander
  - make a linearizer append id to concept

New Transformers
================
- attach (put together this functionality from genitive, adjectives, etc)
- auxiliary verbs (distinguish passive and modal, see negation)
- conjunctions (and, or)
- comparison (larger_than, smaller_than)

General Library
===============
- add unit tests with unittest

Web Service
===========
Get / -> list all configs
