Make the project contents a little bit more attractive

This pull request combines a couple of small edits that should help to improve the appeal of our project a little. Most importantly I added a note to the Readme to repeat that anyone who wants to contribute is welcome, ordered the Dependencies by importance, and replaced the suggestiions in `setup.py` to restart or logoff/login by useful instructions on how to refresh the environment variables.

I still need to check that the command displayed to Windows users is correct.