Add confirmation before closing the window

Fixes #11

www/assets/main.js

@@ -30,7 +30,8 @@
 //optionElements.cursorBlink.addEventListener('change', createTerminal);
 
 //createTerminal();
-
+//
+//
 function createTerminal(name) {
   var terminalContainer = document.getElementById('terminal-' + name);
   // Clean terminal

www/index.html

@@ -78,5 +78,18 @@
 	<script src="/assets/main.js"></script>
         <script src="/assets/xterm.js"></script>
         <script src="/assets/attach.js"></script>
+        <script type="text/javascript" charset="utf-8">
+            window.onbeforeunload = function (e) {
+                e = e || window.event;
+
+                // For IE and Firefox prior to version 4
+                if (e) {
+                    e.returnValue = 'Make sure you saved your session URL';
+                }
+
+                // For Safari
+                return 'Make sure you saved your session URL';
+            };
+        </script>
     </body>
 </html>