Add options and a browser-action popup.

go-back-with-backspace/background.js

+// Copyright 2016 Google Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
 // Put up an informative message on first install.
 chrome.runtime.onInstalled.addListener(function(details) {
   if (details.reason == "install") {
-    chrome.tabs.create({url: "installed.html"});
+    chrome.tabs.create({url: "pages/installed.html"});
   }
 });