Improve doc/README.rst

[WillAyd]

The README within the doc directory still makes a reference to rebasing, though current preferred method is to merge in updates from master. Additionally there is a reference to python make.py build which doesn't do anything by default.

Items here can certainly be improved for clarification to new contributors

[alexander-l-stone]

Hey, I put in a PR with the git process updated. I am not sure it needs the command for setting the upstream, but I included it anyway.

[SeattleChris]

I tried to install based on the instructions in the doc/README.rst. Following the instructions from @alexander-l-stone helps move forward, but there seem to be additional errors in the "Building the documentation" section at this command:
python make.py html
After installing dependencies I eventually got an error that Pandoc was not installed after it was just installed.

[WillAyd]

@ChrisSeattle tough to say from that alone. Could you post the traceback?

[SeattleChris]

I am in a pipenv.

$ python make.py html
Warning: Pandoc is not installed. Skipping notebooks.
Running Sphinx v1.8.1
sphinxcontrib.spelling failed to import with error "No module named 'sphinxcontrib.spelling'". `spellcheck` command is not available.

Extension error:
Could not import extension matplotlib.sphinxext.plot_directive (exception: No module named 'matplotlib')

[WillAyd]

We don't have instructions posted for pipenv. Should be possible though still tough to say without knowing more about your environment. I believe sphinxcontrib.spelling is a warning whereas the error at the end suggests you don't have Matplotlib installed in your virtual environment.

Have you tried the instructions on the more general contributing guide to set up your environment?

https://pandas.pydata.org/pandas-docs/stable/contributing.html#creating-a-python-environment

[datapythonista]

Closing in favor of #23828.