Fixes#122, and adds tests for it:
The problem, I believe, was that some files were deleted before their symlink was deleted. `Unix.stat` fails on symlinks that point to missing files. We don't really care about their stat, honestly, so we can just run `Unix.lstat` and remove them.
* Use variants instead of a boolean
* Add infrastructure for multishell and aliases: Aliases are required because I want to have a default node version on startup
* create alias command
* fmt
* Added aliases (Fixes#29) and opt-in multishell support (Fixes#19)
* Better docs
* update snapshot
* Some/Fail => Some/None
* add lint-staged
* use refmt and all of prettier are grouped
* System.readdir => Fs.readdir (now uses Lwt)
* use lstat for file_exists: check if symlink exists instead of actual linked file. also, initialize the Random seed on Env
* Remove fish set options that were added in trial and error
* Bootstrap script
* add bootstrap documentation