Build documentation references requirements files that don't exist

[fishcorn]

After cloning SMQTK, I'm not able to create a conda environment using either of the following commands:

conda create -n <env_name> --file requirements.conda.txt
pip install -r requirements.pip.txt

even though the documentation explicitly recommends them. Instead I could only run the following:

pip install -r requirements.txt

[Purg]

There is currently a mismatch as to what readthedocs and the current documentation say. There has been a separate issue that has not floated up high enough yet that the readthedocs page is not building the currently documentation source automatically (or there is an error occurring that's preventing the build). Technically, if you build the docs locally, they should show the correct instructions involving the requirements.*.txt files.