only send credentials when using working https URLs

[danp]

It'd be great if there was a way to specify httpie should only send credentials from netrc or similar when https is in use and working. This would help prevent accidentally sending credentials over http when one types http http://foobar.org when they meant http https://foobar.org.

[rwish]

As I know, HTTPie sends credentials only once you deliberately include them in the command