Merge pull request #379 from Eric-Guo/master

Fix Rare case error uninitialized constant AjaxDatatablesRails::ActiveRecord::Base

Author: n-rodriguez

lib/ajax-datatables-rails/base.rb

@@ -3,7 +3,7 @@
 module AjaxDatatablesRails
   class Base
 
-    class_attribute :db_adapter, default: ActiveRecord::Base.connection.adapter_name.downcase.to_sym
+    class_attribute :db_adapter, default: ::ActiveRecord::Base.connection.adapter_name.downcase.to_sym
     class_attribute :nulls_last, default: false
 
     attr_reader :params, :options, :datatable