Add in missing require

Reverse_https handler needs to specifically require reverse_http in
order to ensure that the Msf::Handler::ReverseHttp mixin is available at
run time.

lib/msf/core/handler/reverse_https.rb

@@ -1,6 +1,7 @@
 # -*- coding: binary -*-
 require 'rex/io/stream_abstraction'
 require 'rex/sync/ref'
+require 'msf/core/handler/reverse_http'
 
 module Msf
 module Handler