Indentation-Based Racket Syntax with Macros and Infix Operators

It's experimental, but supports things like the interactive shell I mentioned in this comment: https://news.ycombinator.com/item?id=16879995

Example of a use of the shell library with the special syntax: https://github.com/tonyg/racket-something/blob/master/exampl...

Screencast of an interactive session. Very simple, but shows some of the basics: https://asciinema.org/a/83450