Add tests

• unittest
• discover

    root/
      setup.py
      README.rst
      MANIFEST.in
      bin/
        runmymath.py
        runmymath.bat
      mymath/
        __init__.py
        calc.py
        test/
          __init__.py
          test_all.py
          test_calc.py

#empty (needed for unittest discover)

python mymath/test/test_calc.py
python mymath/test/test_all.py

python -m unittest discover