Patch Liquid to include filters in a predictable order

This brings us a reliable filter override until
https://github.com/Shopify/liquid/pull/87 is accepted and
released upstream.

lib/chili_project/liquid/liquid_ext.rb

@@ -17,6 +17,8 @@ module ChiliProject
     module LiquidExt
       ::Liquid::Block.send(:include, Block)
       ::Liquid::Context.send(:include, Context)
+      # Required until https://github.com/Shopify/liquid/pull/87 got merged upstream
+      ::Liquid::Strainer.send(:include, Strainer)
     end
   end
 end

lib/chili_project/liquid/liquid_ext/block.rb

@@ -19,6 +19,8 @@ module ChiliProject
         def self.included(base)
           base.send(:include, InstanceMethods)
           base.class_eval do
+            unloadable
+
             alias_method_chain :render_all, :cleaned_whitespace_and_cache
           end
         end

lib/chili_project/liquid/liquid_ext/context.rb

@@ -19,6 +19,8 @@ module ChiliProject
         def self.included(base)
           base.send(:include, InstanceMethods)
           base.class_eval do
+            unloadable
+
             alias_method_chain :handle_error, :formatting
           end
         end

lib/chili_project/liquid/liquid_ext/strainer.rb

@@ -0,0 +1,44 @@
+#-- encoding: UTF-8
+#-- copyright
+# ChiliProject is a project management system.
+#
+# Copyright (C) 2010-2011 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# See doc/COPYRIGHT.rdoc for more details.
+#++
+
+# Required until https://github.com/Shopify/liquid/pull/87 got merged upstream
+module ChiliProject
+  module Liquid
+    module LiquidExt
+      module Strainer
+        def self.included(base)
+          base.extend(ClassMethods)
+          base.class_eval do
+            unloadable
+
+            @@filters = []
+          end
+        end
+
+        module ClassMethods
+          def global_filter(filter)
+            raise ArgumentError, "Passed filter is not a module" unless filter.is_a?(Module)
+            @@filters << filter
+          end
+
+          def create(context)
+            strainer = self.new(context)
+            @@filters.each { |filter| strainer.extend(filter) }
+            strainer
+          end
+        end
+      end
+    end
+  end
+end