getText(url, mimeType) {
    let encodedUrl = window.encodeURIComponent(url);
    mimeType = mimeType || mime.lookup(url);
    return this.storage.getItem(encodedUrl).then(function (uint8array) {
      var deferred = new core["defer"]();
      var reader = new FileReader();
      var blob;
      if (!uint8array) return;
      blob = new Blob([uint8array], {
        type: mimeType
      });
      reader.addEventListener("loadend", () => {
        deferred.resolve(reader.result);
      });
      reader.readAsText(blob, mimeType);
      return deferred.promise;
    });
  }
Get Text from Storage by Url
@param  {string} url
@param  {string} [mimeType]
@return {string}