Example renewal: aioxmpp

This is how it works in a nutshell (see the readme for details!)::

  $ cd data/
  $ ./update-entry.py libraries.json aioxmpp
  old entry:
  {
      "info": [
          "Python"
      ],
      "last_renewed": null,
      "name": "aioxmpp",
      "url": "https://github.com/horazont/aioxmpp"
  }

  new entry:
  {
      "info": [
          "Python"
      ],
      "last_renewed": "2017-03-16T07:33:04",
      "name": "aioxmpp",
      "url": "https://github.com/horazont/aioxmpp"
  }
  is this okay? [y/n]y
  $ git commit -pv

data/libraries.json

@@ -13,7 +13,7 @@
         "info": [
             "Python"
         ],
-        "last_renewed": null,
+        "last_renewed": "2017-03-16T07:33:04",
         "name": "aioxmpp",
         "url": "https://github.com/horazont/aioxmpp"
     },