code: function minjs(config, tools) {
    return tools.simpleStream(config, [
      config.concat && concat(config.concat),
      config.minify && uglify(config.uglifyjs)
    ])
  }
docs: Make a simple JS build, optionally concatenated and minified
  @param {object} config - task configuration
  @param {object} tools - gtm utility functions
  @return {object}