code: def create_folder(opts)
        opts = opts.clone
        req = build_soap! do |type, builder|
          if(type == :header)
          else
            builder.nbuild.CreateFolder {|x|
              x.parent.default_namespace = @default_ns
              builder.parent_folder_id!(opts[:parent_folder_id])
              builder.folders!(opts[:folders])
            }
          end
        end
        do_soap_request(req)
      end
docs: ------------- Folder Operations ------------
   Creates folders, calendar folders, contacts folders, tasks folders, and search folders.
   @see http://msdn.microsoft.com/en-us/library/aa563574.aspx CreateFolder
  
   @param [Hash] opts
   @option opts [Hash] :parent_folder_id A hash with either the name of a
     folder or it's numerical ID.
     See: http://msdn.microsoft.com/en-us/library/aa565998.aspx
     {:id => :root}  or {:id => 'myfolderid#'}
   @option opts [Array<Hash>] :folders An array of hashes of folder types
     that conform to input for build_xml!
     @example [
       {:folder =>
         {:display_name => "New Folder"}},
       {:calendar_folder =>
         {:folder_id => {:id => 'blah', :change_key => 'blah'}}}