Move Countable out of resources

lib/shopify_api.rb

@@ -13,5 +13,6 @@ end
 
 require 'shopify_api/events'
 require 'shopify_api/metafields'
+require 'shopify_api/countable'
 require 'shopify_api/resources'
 require 'shopify_api/session'

lib/shopify_api/resources.rb

@@ -1,4 +1,3 @@
-require 'shopify_api/resources/countable'
 require 'shopify_api/resources/base'
 require 'shopify_api/resources/application_charge'
 require 'shopify_api/resources/article'