code: function(path, callbackSuccess, callbackError) {
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
      if (xhr.readyState === 4) {
        if (xhr.status >= 200 && xhr.status < 300) {
          callbackSuccess(xhr.responseText);
        } else {
          callbackError();
        }
      }
    };
    xhr.open('GET', path, false);
    try {
      xhr.send();
    } catch (e) {
      callbackError();
    }
  }
docs: Fetches the content of a file through AJAX.
  @param {string} path the path of the file to fetch
  @param {Function} callbackSuccess
  @param {Function} callbackError