installation instructions can be improved for non-python users

[necozay]

I tried doing a TuLiP installation from scratch on a wiped out Mac. I found the following poitns a bit confusing in installation instructions (this could be because of the strange access rights on Mac).

• User access rights are not clear in installation instructions. Is it assumed that everything is done in sudo? We might want to clarify this.
• I started getting pip and installed it for --user.
• pip install tulip did not work after getting pip as setuptools clashes with the one that comes with Mac python distribution.
• My attempt to upgrade setuptools with pip also failed due to an EnvironmentError
• I finally installed virtualenv and installed tulip in a virtualenv with pip
• Then, I kept reading the instructions in https://pypi.org/project/tulip/. To check the dependencies, it says I should call tulip.interfaces.print_env() but it is not clear where I should call this. Maybe we should mention that this can be called from within python.
• It also says "A test suite is provided under tests/." but if I use pip for installation, does this folder exist? Maybe we should say, this is for when one installs from the source.

Some of the above points are clearer in the user documentation https://tulip-control.sourceforge.io/doc/install.html where a distinction between PyPi and installing from source is made. Just thought I would write these down in case it is useful for someone else.

[slivingston]

while treating this issue, consider switching to Pipenv