Run `npm install`.

@param  {Array}   dependencies	[string names of all your dependencies, plus versions if you want, you know the drill]
@param  {Object}   options
@param  {Object|Function} cb
function(options, cb) {
    return doNpmCommand({
      npmCommand: 'install',
      cmdArgs: options.dependencies,
      cmdOptions: {
        production: options.production || false,
        loglevel: options.loglevel || undefined,
        save: options.save || false,
        'save-dev': options.saveDev || false,
        'save-exact': options.saveExact || false,
        prefix: options.prefix || undefined,
      },
      dir: options.dir
    }, cb);
  }