Added check and conversion for non-numerical data coming in to sig_fig_round

[connorferster]

I tried running the new version to see the new PyVista display. It took some work. Once I got the installs figured out, I found that there seemed to be a bug in the function sig_fig_round. It was being passed a text_label and it was trying to perform math functions on the value. It seemed that a conversion step was necessary to convert the text_label to a float.

I added the conversion into sig_fig_round and then the display worked. And...it looks nice! I love that it is not spawning a separate process that hangs your kernel like VTK does. Thank you!

[JWock82]

Thanks Connor. As Pyvista is a new feature, there may still be a few bugs in there I have not caught yet. Keep an eye out for them. It's been a major improvement to the rendering code. Much simpler to implement than directly using VTK which required me to manage the whole rendering pipeline. Pyvista manages all that for you. This will make future development of the rendering code much simpler.