Convert to Python 3

[mhijazi1]

The main reason pbot was python 2 was due to an incompatibility with the slackclient package. This has been resolved, convert to python 3.

This blocks all future dev work and should be done first.

[Litagano-M]

I'd imagine this is pretty important

I suppose the best way to go about this would be to run this in Python 3 and see what breaks?

[maren-mclean]

Actually we have an internal build working on Python 3 for a work, a few features stripped but we are working on it! PantherBot was the base, give it a few days and it should be up.

[maren-mclean]

*for work