readthedocs alters docs/conf.py which in turn means python_scm detects a
version and incorrectly adjusts the version number. Here we try to work
around this problem.

We do this by renaming the docs/conf.py file and copying it back to
docs/conf.py when setup.py is invoked. This way, hopefully, scm won't
see the changes to docs/conf.py

References:
http://stackoverflow.com/questions/35811267/readthedocs-and-setuptools-scm-version-wrong/36386177
https://github.com/pypa/setuptools_scm/issues/84