I'm attempting to make a defacto standard for specifying Chrome App dependency substitutions using the `"chromeapp"` field in `package.json`.

The `"chromeapp"` field is just like the [`"browser"` field in `package.json`](https://github.com/defunctzombie/package-browser-field-spec) except it's intended for Chrome Apps instead of a generic browser environment. Bundler tools like `browserify` or `webpack` can be configured to look for the `"chromeapp"` field instead of the `"browser"` field when doing a build for a Chrome App.

In this specific package, since Chrome Apps can use raw sockets we want to replace e.g. `require('net')` with `require('chrome-net')`.