Add support for HTTP proxies.

SOAPpy does some low-level HTTP request manipulation and needs to be
explicitly aware of HTTP proxies, which also have to be formatted for
its consumption (without a schema or path).

Closes Debian bug #708516 (and its duplicates).
Merge branch 'add-http-proxy-support' of git://github.com/rakuco/python-debianbts into httpproxy
Fixed whitespace
Merge branch 'httpproxy'