Add ipywidgets

Created by: derkling

Here are the few changes I've found useful to enable ipywidgets in JupyterLab.

If they are installed/enabled correctly, this notebook should just work: https://github.com/jupyter-widgets/ipywidgets/blob/e27c7a81fd7ff96ea74726575845b61e81c5c855/docs/source/examples/Using%20Interact.ipynb