Redirect URL: support existing params

$url = "http://blah.com?x=y" . "?Z=" . $value;
will obviously not work because the query part of the url now has two ?s

Previously if your url already contained query params, the generated url
would be incorrect.
Merge url-support-parameters (#2) into master

Redirect URL: support existing params

$url = "http://blah.com?x=y" . "?Z=" . $value;
will obviously not work because the query part of the url now has two ?s

Previously if your url already contained query params, the generated url
would be incorrect.