Include Python version requirements and compatibilities in README

[hlapp]

I thought they are there, but I can't find them in the document, nor do they seem linked. If you think it's too much clutter there, consider using the wiki of the repo and then link to it from the README?

[johnbradley]

The third line in README.md has the python version requirements.

Runs on Python 2.7 or 3.5.

[hlapp]

Right, but that's far from the whole story, right?

[johnbradley]

The requirement is a python 2.7+ version with a functioning ssl module.
If they have python 2.7.9+ or 3.5+ it will work.
The Redhat patched python 2.7.8 also works.
There is this guide to fix the ssl module: https://urllib3.readthedocs.io/en/latest/user-guide.html#ssl-py2, but in practice I have seen this fail to install.
There are also recommendations online to run pip install pyopenssl ndg-httpsclient pyasn1, these have also failed for me. root may be required to install additional dependancies needed by these fixes.

The error with a non-functioning ssl module:

InsecurePlatformWarning: A true SSLContext object is not
available. This prevents urllib3 from configuring SSL appropriately and 
may cause certain SSL connections to fail. For more information, see 
https://urllib3.readthedocs.org/en/latest  
/security.html#insecureplatformwarning.

I don't want to kludge up the README with all of this. I will look into using the wiki and put a quick blurb in the README. I have been meaning to write down all the ~/.ddsclient config options so this can go in the wiki as well.