Rewrite AbstractHTTPHandler to use modern httplib interface.

Rewrite AbstractHTTPHandler to use modern httplib interface.

The chief benefit of this change is that requests will now use
HTTP/1.1 instead of HTTP/1.0.  Bump the module version number as part
of the change.

There are two possible incompatibilities that we'll need to watch out
for when we get to an alpha release.  We may get a different class of
exceptions out of httplib, and the do_open() method changed its
signature.  The latter is only important if anyone actually subclasses
AbstractHTTPHandler.