* remove all of the "from __future__" imports
* remove the first batch of rdkit.six imports/uses
* next step of rdkit.six removal
* removing xrange, range, and some maps
* next round of removals
* next round of cleanups
* fix inchi test
* last bits of "from rdkit.six" are gone
* and the last of the six stuff is gone
* strange importlib problem
* Fix 2D/3D interpretation of V2000 ctabs
* Remove debugging statements
* Apply fix to V3000 molblock
* Add 3D pretending to be 2D test case
* Fix for review comments.
