Require that the subdirectory in site-lisp match the formula name
exactly. This lets us provide better information in the caveats and
will make it easier for helper methods to write to the correct
location (as in in Homebrew/homebrew-emacs#13).
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.