Fix indent for `module`.
Add indent for `for/sum` and `for*/sum`.
Add more racket-builtins keywords.
Add `racket-test` to run tests in *racket* buffer.

Note: Some cases where this is buggy with our sandbox evaluator.
Our sandbox eval's `run!` doesn't need file touched, just saved.
Use *shell*
Call `racket-mode-variables`.