Toggle httplib logging with http_debug argument

Adds an `http_debug` argument to `Client`, which defaults to `False`. This
parameter is passed to `Connection`. If `http_debug` is `True`, the
`debuglevel` of the `httplib` `Connection` is set to `1`.

This effectively decouples `httplib`'s debug statements from the
debugging level of the application.
merged in changed on how httplib debug is triggered