npm.load() must be called before any other function call. Both parameters are
optional, but the second is recommended.
The first parameter is an object containing command-line config params, and the
second parameter is a callback that will be called when npm is loaded and ready
The first parameter should follow a similar structure as the package.json
For example, to emulate the --dev flag, pass an object that looks like this:
For a list of all the available command-line configs, see npm help config