code: function changed (targetDir) {
    return async function changeTester (customizeResult) {
      const result = await deep(mapFiles(customizeResult, targetDir, require('./lib/changed')))
      return {
        changed: values(result).indexOf(true) >= 0,
        files: result
      }
    }
  }
docs: Creates a function that asserts that the result of the `customize#run()` method to produces the same
  contents as found on the disk. The returned promise is rejected, if this is not the case.s
  
  @function
  @param {string} targetDir path to the target directory
  @returns {function(object):Promise<{unchanged:boolean, files: string[]}>} return a function that writes a customize-result to the targetDir.
  The function takes a customize-result as first parameter and returns a promise for a list of filenames.
  (i.e. the files that were checked)
  @public