docs: function readFile(filepath, callback) {
          window.requestFileSystem(
              LocalFileSystem.PERSISTENT,
              0,
              function(fileSystem) {
                  fileSystem.root.getFile(
                      filepath,
                      null,
                      function gotFileEntry(fileEntry) {
                          fileEntry.file(
                              function gotFile(file) {
                                  var reader = new FileReader();
                                  reader.onloadend = function(evt) {
                                      // #72 - Fix WP8 loading of config.json
                                      // On WP8, `evt.target.result` is returned as an object instead
                                      // of a string. Since WP8 is using a newer version of the File API
                                      // this may be a platform quirk or an API update.
                                      var text = evt.target.result;
                                      text = (typeof text === 'object') ? JSON.stringify(text) : text;
                                      callback(null, text); // text is a string
                                  };
                                  reader.readAsText(file);
                              },
                              function(error) {
                                  callback(error);
                              }
                          );
                      },
                      function(error) {
                          callback(error);
                      }
                  );
              },
              function(error) {
                  callback(error);
              }
          );
      }