code: 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);
    }
docs: 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