Conform to package.el format standards

This is the minimal amount necessary to be able to get npm.el into MELPA (https://github.com/milkypostman/melpa).

There's plenty more that can/should be done (`byte-compile-file` produces warnings, most of those `setq` calls should be `defcustom`, etc.), but I'll send pull requests for those another day. =)

(Also, it'd be awesome if your emacs.js used package.el + MELPA instead of git submodules; it's the future!)