Remove IPython as a dependency

[erik-hasse]

Is your feature request related to a current problem? Please describe.
Currently IPython is listed as a dependency, but only a single method is used. IPython adds a lot of transitive dependencies, some of which vary by platform (mac vs linux) which makes annoying to use in production environments.

Describe proposed solution
Remove IPython from the list of dependencies and make it an optional import in the utils.py file linked above:

try:
    from IPython import get_ipython
except ModuleNotFoundError:
    get_ipython = None

Then add a simple check at the top of the _is_notebook function:

if get_ipython is None:
    return False

Describe potential alternatives
None

Additional context
I can open a PR with the change if this seems reasonable.

[hrzn]

Hi @erik-hasse, thanks for the suggestion, I agree it'd make sense. We would be very open to receiving a PR for this.