Add :like case for :conf, use nil as default value in the switch

Author: Nicolas Rodriguez

lib/ajax-datatables-rails/datatable/column.rb

@@ -121,8 +121,10 @@ def non_regex_search
           casted_column.matches("#{formated_value}%")
         when :end_with
           casted_column.matches("%#{formated_value}")
-        else
+        when :like
           casted_column.matches("%#{formated_value}%")
+        else
+          nil
         end
       end