fix(cypress): add polyfill for cypress open

`cypress run` is ok but `cypress open` fails due to lack of support of:
- Array.prototype.includes
- Object.entries

package.json

@@ -37,6 +37,7 @@
     "invariant": "^2.2.3",
     "js-md5": "^0.7.3",
     "material-ui": "^1.0.0-beta.43",
+    "mdn-polyfills": "^5.5.0",
     "prop-types": "^15.6.1",
     "react": "^16.3.2",
     "react-dom": "^16.3.2",

src/index.js

@@ -2,6 +2,10 @@ import React from "react";
 import ReactDOM from "react-dom";
 import { MuiThemeProvider, createMuiTheme } from "material-ui/styles";
 
+// cypress:open doesn't support the following, we need to pollyfill ...
+import "mdn-polyfills/Array.prototype.includes";
+import "mdn-polyfills/Object.entries";
+
 import "./index.css";
 import RootContainer from "./containers/RootContainer";
 import registerServiceWorker from "./registerServiceWorker";