Quickstart tutoirial - without jupyter notebook

[DanielAndreasen]

Hi again,

I've tried running the quickstart tutorial (https://gollum-astro.readthedocs.io/en/latest/quickstart.html) from ipython (not notebook), and I don't get a plot after running the commands:

ax = normalized_spectrum.plot()
ax.set_ylim(0, 2)

It might be my setup, but are you able to do so? Do I need to change something compared to the jupyter notebook code?

I am able to produce the plots without problems in the notebook though.

Review link: https://github.com/openjournals/joss-reviews/issues/6601