Require rex/socket/ssl in framework.rb

Add an explicit require for the new socket/ssl.rb in framework.rb
in case it has not yet been loaded.

This should address the Travis failure on initial PR, although the
gem version in socket has not been updated, so this might take a
bit to propagate. In the end, if the dependency already gives us
this functionality by the time we call Rex::Socket::Ssl then this
commit can safely be dropped

lib/msf/core/framework.rb

@@ -61,6 +61,7 @@ module Offspring
   require 'msf/core/db_manager'
   require 'msf/core/event_dispatcher'
   require 'rex/json_hash_file'
+  require 'rex/socket/ssl'
 
   #
   # Creates an instance of the framework context.