Redundancy: requirements.txt and setup.py

[dgahle]

Package installation using the setup.py checks for package dependencies required (pandas, six, python-pptx) and installs them if missing. Thus installing the same modules from requirements.txt is redundant.

requirements-tests.txt could be made redundant by adding {} to setup.py as well. Though I appreciate that you might want to keep these separate.

I would be happy to make the change and submit a PR.