Apply some of the techniques from https://caremad.io/2014/11/distributing-a-cffi-project/ in the hope of making 'pip install' work reliably for pynacl
Don't bother trying to work out which commands require cffi and which do not as 'use_system' is called for all of them
Cosmetic formatting fix
Fix the import order in setup.py
Merge pull request #115 from NegativeMjark/cffi_setup_fixes

Apply some of the techniques from https://caremad.io/2014/11/distribu… … …ting-a-cffi-project/