Add support to merge user API

Author: pocke

lib/zendesk_api/resources.rb

@@ -682,6 +682,8 @@ def clear_sessions
  false
  end
 
+ put :merge
+
  has CustomRole, :inline => true, :include => :roles
  has Role, :inline => true, :include_key => :name
  has Ability, :inline => true