fix pip and python 3

[johannjacobsohn]

1. Geonum cannot be installed atm, adding the appropriate Manifest file fixes that issue.

$ pip install --user geonum

Collecting geonum
  Using cached https://files.pythonhosted.org/packages/07/5c/690435f33dcd8905df4edcb99c16835fd8d528420dff99ce74cb62ae89a5/geonum-1.3.1.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-oKoXlR/geonum/setup.py", line 12, in <module>
        with open("VERSION.rst") as f:
    IOError: [Errno 2] No such file or directory: 'VERSION.rst'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-oKoXlR/geonum/

2. The handling of comparing None to a number (eg. with the < operator) has changed between python 2 and 3 (returning false vs raising exception). Two commits to fix the bug and add a test case reproducing the issue.