Ensure Black formatting

[lbianchi-lbl]

While working on #128, I realized that even though black is part of the dev dependencies:

1. There's no check enforced by the CI
2. The codebase (or at least a large portion of it) has not been formatted with Black (i.e. if one runs black ., 171 files are reformatted)

Before the upcoming release, we should:

• Update the Black version in requirements-dev.txt to match the one used in idaes-pse
• Add a Black formatting check to the CI
• Run black . on the entire repository (including Jupyter notebooks)

[bpaul4]

@lbianchi-lbl I think this is a great idea, however I'm wary of what black will do to JSON- and HTML-like code in .ipynb files. Let me know if I can assist with this effort at all.