[WIP] Swift reboot

Updating presentation for Swift, and trying to address the feedback in #21. Anything in all caps is a note for myself about something that still needs to be done.

The presentation itself is in [Deckset](decksetapp.com) format now, intended for use with the “Next” theme.

- [Source Markdown](https://github.com/jspahrsummers/enemy-of-the-state/pull/22/files#diff-75)
- [Rendered PDF](https://github.com/jspahrsummers/enemy-of-the-state/raw/reboot/Enemy%20of%20the%20State.pdf) (does not include presenters' notes, and may be a couple revisions behind)

Comments welcome! :heart::bow:

**To do:**

 - [ ] Add code samples where missing
 - [ ] Add presenters' notes where missing
 - [ ] Audit apostrophes and quotation marks
 - [ ] Think hard about ordering
But, stateless globals. A library’s API consists entirely of global symbols.

Huge :+1: for “avoid shared mutable state,” and “avoid singletons.” But :-1: for “globals are the enemy,” since Swift actively prevents you from using locals for e.g. building recursive parsers (context-free rather than regular grammars); i.e. you have to pick: globals (probably appropriate for parsers-as-API, which they generally are), lazy properties (messy), or manual two-step init (unreadable, messy, stateful).

Otherwise put: I think we should encourage people to use `let x = …combinators…` if it’s a clearer way of writing the thing than `func x(…)`. “Just Say No” should draw a clear distinction between immutable globals and shared state.