code: function relativePathArray(filePath, fromPath) {
    filePath = path.normalize(filePath);
    fromPath = path.normalize(fromPath);
    if (filePath.indexOf(fromPath) === -1 || filePath === fromPath) {
      // TODO Error handling: this should cause a warn
      return [];
    }
    const keys = path.relative(fromPath, path.dirname(filePath));
    if (keys && keys.length !== 0) {
      return keys.split(path.sep);
    }
    return [];
  }
docs: Given a file's path and a string representing a directory name,
  return an Array that only contains directories at or beneath that
  directory.
  
  @example relativePathArray('/foo/bar/baz/ding/dong/tink.txt', 'baz')
  // -> ['baz', 'ding', 'dong']
  @param {String} filePath
  @param {String} fromPath
  @return {Array}