document.close after document.write

Fixes #6

https://stackoverflow.com/questions/12595819/ff-keeps-spinning-after-doc
ument-write

example.html

@@ -157,6 +157,7 @@
         var plainHTML = CryptoJS.AES.decrypt(encryptedHTML, passphrase).toString(CryptoJS.enc.Utf8);
 
         document.write(plainHTML);
+        document.close();
     });
 </script>
 </body>

password_template.html

@@ -156,6 +156,7 @@
         var plainHTML = CryptoJS.AES.decrypt(encryptedHTML, passphrase).toString(CryptoJS.enc.Utf8);
 
         document.write(plainHTML);
+        document.close();
     });
 </script>
 </body>