Add link to ITS Jupyter hub in setup #76

Currently the setup instructions point at the instructions for the Intro to Python course, which are fine for demonstrating other ways of setting up a python interpreter. We could also simply add the current link to the ITS Jupyter hub as well.

Alternatively, if we don't want to add this link to the course notes (e.g. because you never know when the address might change) then we could simply add it to the slides at the beginning of the course instead (e.g. as part of #57).