Add more documentation to README or elsewhere

[nbowden045]

Some documentation that might help new users or developers are the following items:

• Details about how to run the application:
• Format specification for the Groups.csv:
• Installation requires / requirements.txt file:

Running the application
Add something that says to run by doing

python src/csvgrader/mainGUI.py

Groups.csv format
What columns/column titles should this CSV have, are multiple individuals listed on a given row for one group or is each individual on their own row with another column specifying a group identifier?

Install requires
It looks like this is in the pyproject.toml, although it should not say "tkinter" as tkinter is a builtin python module, already present, and so pip install fails if it tries to download tkinter from PyPI.

Maybe also a requirements.txt file specifying all versions of packages which a built version works against would be good. When I did the install,
pip looked for:

• pandas
• numpy
• python-dateutil
• pytz
• tzdata
• six
  And of course install also requires setuptools