switch localStorage mock to mock-local-storage,

fix unit tests to work with ES6 import syntax,
remove testenv module

source/assets/scripts/localStorage.js

@@ -1,6 +1,3 @@
-//
-//module.exports = {getReviewsFromStorage, saveReviewsToStorage};
-
 /**
  * @returns {Array<Object>} An array of reviews found in localStorage
  */