Fixes #6993: Allow repo-discovery through a proxy.

Note that the Anemone gem allows the passing of proxy_host and proxy_port
by default but does not currently support proxy user and password.
In order to get around this, a monkey patch is applied to anemone
to allow passing user and port.
Merge pull request #4549 from ehelms/fixes-6993

Fixes #6993: Allow repo-discovery through a proxy.