Fix bug: TypeError can't convert Fixnum into String

wmap_target_port is retrieved from datastore['RPORT'], and that's a
Fixnum. But wmap_base_url is treating that like a String, so when a
module uses that function, it's doomed.

See:
http://dev.metasploit.com/redmine/issues/7748

Author: sinn3r

lib/msf/core/auxiliary/wmapmodule.rb

@@ -71,7 +71,7 @@ def wmap_base_url
 		else
 			res << datastore['VHOST']
 		end
-		res << ":" + wmap_target_port
+		res << ":" + wmap_target_port.to_s
 		res
 	end