code: function _write(filePath, json) {
          var result = $.Deferred(),
              _file = FileSystem.getFileForPath(filePath);
  
          if (_file) {
  
              var content = JSON.stringify(json);
              FileUtils.writeText(_file, content, true)
                  .done(function () {
                      result.resolve();
                  })
                  .fail(function (err) {
                      result.reject();
                  });
  
          } else {
              result.reject();
          }
  
          return result.promise();
      }
docs: Performs the write of JSON object to a file.
  @param   {string} filepath - path to JSON file
  @param   {object} json  - JSON object to write
  @returns {$.Deferred} - a jquery deferred promise,
  that is resolved with the write success or failure