Run python nosetests using a watcher for changes on Linux

Apparently, this is very specific to linux (at least Ubuntu 18.04) as I tried using the "nose-watch" package and it did not work. Ultimately, I did this:

sudo -H pip install nose-watcher
nosetests --with-watcher

Also, if you plan to run it in another window you will need to reload or open a new shell post install.