Migrate glance-replicator to requests for HTTPS Support

As operators and users become more security conscious, it is important to
support deployments of Glance served only over HTTPS. In its current state,
``glance-replicator`` uses ``httplib`` and thus does not properly verify
HTTPS connections. This allows for various and very serious attacks to be
performed while the user of ``glance-replicator`` attempts to communicate with
Glance.