Explicitly add default host & port to app.run function

I decidedto add this because the way to change the host & port may not be
immediately obvious to everyone.

runserver.py

@@ -1,3 +1,5 @@
 #!env/bin/python
 from i2p2www import app
-app.run(debug=False)
+
+if __name__ == '__main__':
+    app.run(host='127.0.0.1', port=5000, debug=False)