Improve the styling of text/stream outputs in notebooks

[stevejpurves]

In a jupyter notebook, natively these will appear as simple black text with no background and rendered in a monospace font.
So doing something similar here would be good. We could also consider also enclosing it in a bounding box / block outline.

An example of a notebook with problematic output is here:
https://curvenote.com/@prisae/emg3d-as-solver-for-simpeg/simpeg-emg3d-inversion-automatic-grid

TODO:

1. improve basic styling - align with juypter
2. prevent unnecessary scrollbars

[stevejpurves]

this is now fixed!