Allow acceptance of invalid ssl certificates

[scaryclam]

This was originally requested here: http://sourceforge.net/p/python-webdav/feature-requests/10/

[Crypt0s]

I am the original requester:

I'm working on a patch--apparently httplib2 is bugged because my patch wasn't working for me despite it being the official method to accept non-valid certs. See bug here: https://code.google.com/p/httplib2/issues/detail?id=173

I'll submit another diff in a bit.