Fix the Strainer patch to enforce a filter array

Up until now, the patch used to be a no-op. While the filters class
attribute was set correctly, the methods using it were not actually
overridden as they are only included above the existing methods in
the module chain.

This resulted in an arbitrary load order of filters on Ruby 1.8. As
such, our overridden standard filters might not have actually
overridden anything.

Still, the patch can be completely removed once we either require
Ruby 1.9 (as we have ordered ahshes by default then) or once
https://github.com/Shopify/liquid/pull/87 was merged and released
upstream.

lib/chili_project/liquid/liquid_ext/strainer.rb

@@ -21,18 +21,23 @@ module ChiliProject
           base.extend(ClassMethods)
 
           base.class_attribute :filters, :instance_reader => false, :instance_writer => false
-          base.class_eval <<-RUBY, __FILE__, __LINE__ + 1
-            self.filters = @@filters.values
-          RUBY
+          base.class_eval do
+            self.filters = base.send(:class_variable_get, '@@filters').values
+
+            class << self
+              alias_method_chain :global_filter, :filter_array
+              alias_method_chain :create, :filter_array
+            end
+          end
         end
 
         module ClassMethods
-          def global_filter(filter)
+          def global_filter_with_filter_array(filter)
             raise ArgumentError, "Passed filter is not a module" unless filter.is_a?(Module)
-            filters += [filter]
+            self.filters += [filter]
           end
 
-          def create(context)
+          def create_with_filter_array(context)
             strainer = self.new(context)
             filters.each { |filter| strainer.extend(filter) }
             strainer