New logic for making https requests through a proxy

Detect the case where $request_is_to_proxy is true *and* the
$uri->scheme is 'https': ensure that we use Net::HTTP::NB to make a
non-SSL connection to the proxy and then let that handle the HTTPS side
of things by ensuring the scheme is passed in the GET request correctly.
Merge pull request #6 from kaoru/master

HTTPS + Proxy