Version 2.0
o Separate out unit tests, support both py.test and direct execution
o Clean up greenery interface, allways supplying a __version__, and
  identifying all sub-modules for 'from greenery import *'.
o Provide a GNU 'make' file, to illustrate and run all tests
Implement and test v1 backward compatibility
o Add greenery.v1 interface that does exactly what 'import greenery' did
o Implement v1_test.py unit tests
o Complete moving of greenery.fsm unit tests into fsm_test.py.
o Document recommended usage, and techniques to safely support v1.x code
Merge branch 'feature-version-2'