- Renamed basic assertions test for readability, clarity.

- Didn't specify minor Python versions (just 2 and 3).
- Removed test make target, instead use tox.
- The make clean target removes just unshare/constants.py now.
- Removed testing packages from dev dependencies and the test dependency list,
  dev depends just on tox (the other packages are install in the virtualenv).
- Cleaned tox.ini a bit.