Use ssl protocol SSLv23 instead of SSLv3

Apple's sandbox server appears to only work with TLSv1 but not SSLv3.
So use SSLv23 which is more compatible (but, with newer SSL versions,
isn't supposed to actually use the insecure SSLv2 [1]).

[1] http://www.heikkitoivonen.net/blog/2010/08/23/ssl-in-python-2-7/