Adding end-to-end tests

The first test is testing a tricky cache scenario with the back when testing variables.
The end-to-end package used is testcafe.

tests/.testcaferc.js

@@ -0,0 +1,12 @@
+const BROWSER = process.env.BROWSER || "chrome --use-fake-device-for-media-stream";
+
+module.exports = {
+  "browsers": BROWSER,
+  "hostname": "localhost",
+  "skipJsErrors": true,
+  "src": "tests/",
+  "screenshots": {
+    "path": "screenshots/",
+    "takeOnFails": true
+  }
+}