base64.encodestring deprecation warning

[tirkarthi]

base64.encodestring raises DeprecationWarning and has been deprecated since Python 3.1 . base64.encodebytes can be used to fix the warning.

https://github.com/cdent/paste/blob/5a542da992618e30a508f7f03259f63cf2ee1ceb/paste/auth/cookie.py#L147

[cdent]

If you could provide a pull request for this one too, that would be great. Thanks.

[tirkarthi]

Sure, I will add a PR for the two issues I have created. Thanks.