Alex Alegre

This could be a 'chapter 4: getting started in ~~2020~~ \'; possible contents include: - An overview of compilers, implementations, & successor ml standards - [Smackage](https://github.com/standardml/smackage) - [smlpkg](https://github.com/diku-dk/smlpkg) - Editors...

Upgrade to Catlab 0.17

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This PR: 1. Disables some functionality (Rewriting, `n_stratify`), integrating #141, which this supersedes * `n_stratify` is not used in any examples and appears to be primarily to make stratification easier...