.aliases: Add `jsc` alias

Useful for testing code in JavaScriptCore.

Hat tip: https://twitter.com/RussB/status/420409644117262336 (via @rauschma)
.functions: Make `np` remove `node_modules`

This lets you catch cases where you forgot to add a dependency to `package.json`.

Closes #321.
.osx: Support multiple `systemuiserver` pref files

Closes #319.
Merge upstream

* upstream/master:
  .osx: Support multiple `systemuiserver` pref files
  .functions: Make `np` remove `node_modules`
  .aliases: Add `jsc` alias