[MODEL] Use ActiveSupport#delegate instead of stdlib's Forwardable

Prevent failures when `ActiveSupport#delegate` is used, e.g. in an ActiveRecord model:

    class Article < ActiveRecord::Base
      delegate :size, to: :comments, prefix: true
    end

See: http://api.rubyonrails.org/classes/Module.html#method-i-delegate

Closes elastic#6

Author: karmi

elasticsearch-model/elasticsearch-model.gemspec

@@ -22,6 +22,7 @@ Gem::Specification.new do |s|
   s.rdoc_options      = [ "--charset=UTF-8" ]
 
   s.add_dependency "elasticsearch",       '> 0.4'
+  s.add_dependency "activesupport",       '> 3'
   s.add_dependency "hashie"
 
   s.add_development_dependency "bundler", "~> 1.3"

elasticsearch-model/examples/activerecord_associations.rb

@@ -3,6 +3,11 @@
 #
 # https://github.com/rails/rails/tree/master/activerecord
 # http://guides.rubyonrails.org/association_basics.html
+#
+# Run me with:
+#
+#     ruby -I lib examples/activerecord_associations.rb
+#
 
 $LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
 
@@ -81,6 +86,8 @@ class Article < ActiveRecord::Base
   has_many                :comments
 end
 
+class Article < ActiveRecord::Base; delegate :size, to: :comments, prefix: true; end
+
 class Comment < ActiveRecord::Base
   belongs_to :article, touch: true
 end

elasticsearch-model/lib/elasticsearch/model.rb

@@ -1,10 +1,8 @@
-require 'forwardable'
-
 require 'elasticsearch'
 
 require 'hashie'
 
-require 'elasticsearch/model/support/forwardable'
+require 'active_support/core_ext/module/delegation'
 
 require 'elasticsearch/model/version'
 
@@ -105,14 +103,15 @@ def as_indexed_json(options={})
 
         # Delegate important methods to the `__elasticsearch__` proxy, unless they are defined already
         #
-        extend  Support::Forwardable
-        forward :'self.__elasticsearch__', :search        unless respond_to?(:search)
-        forward :'self.__elasticsearch__', :mapping       unless respond_to?(:mapping)
-        forward :'self.__elasticsearch__', :mappings      unless respond_to?(:mappings)
-        forward :'self.__elasticsearch__', :settings      unless respond_to?(:settings)
-        forward :'self.__elasticsearch__', :index_name    unless respond_to?(:index_name)
-        forward :'self.__elasticsearch__', :document_type unless respond_to?(:document_type)
-        forward :'self.__elasticsearch__', :import        unless respond_to?(:import)
+        class << self
+          delegate :search,        to: :__elasticsearch__ unless respond_to?(:search)
+          delegate :mapping,       to: :__elasticsearch__ unless respond_to?(:mapping)
+          delegate :mappings,      to: :__elasticsearch__ unless respond_to?(:mappings)
+          delegate :settings,      to: :__elasticsearch__ unless respond_to?(:settings)
+          delegate :index_name,    to: :__elasticsearch__ unless respond_to?(:index_name)
+          delegate :document_type, to: :__elasticsearch__ unless respond_to?(:document_type)
+          delegate :import,        to: :__elasticsearch__ unless respond_to?(:import)
+        end
 
         # Mix the importing module into the proxy
         #

elasticsearch-model/lib/elasticsearch/model/response.rb

@@ -14,9 +14,8 @@ class Response
                     :took, :timed_out, :shards
 
         include Enumerable
-        extend  Support::Forwardable
 
-        forward :results, :each, :empty?, :size, :slice, :[], :to_ary
+        delegate :each, :empty?, :size, :slice, :[], :to_ary, to: :results
 
         def initialize(klass, search, options={})
           @klass     = klass

elasticsearch-model/lib/elasticsearch/model/response/pagination.rb

@@ -20,8 +20,8 @@ def self.included(base)
             Elasticsearch::Model::Response::Results.__send__ :include, ::Kaminari::PageScopeMethods
             Elasticsearch::Model::Response::Records.__send__ :include, ::Kaminari::PageScopeMethods
 
-            Elasticsearch::Model::Response::Results.__send__ :forward, :response, :limit_value, :offset_value, :total_count
-            Elasticsearch::Model::Response::Records.__send__ :forward, :response, :limit_value, :offset_value, :total_count
+            Elasticsearch::Model::Response::Results.__send__ :delegate, :limit_value, :offset_value, :total_count, to: :response
+            Elasticsearch::Model::Response::Records.__send__ :delegate, :limit_value, :offset_value, :total_count, to: :response
 
             base.class_eval <<-RUBY, __FILE__, __LINE__ + 1
               # Define the `page` Kaminari method

elasticsearch-model/lib/elasticsearch/model/response/records.rb

@@ -10,8 +10,7 @@ module Response
       class Records
         include Enumerable
 
-        extend  Support::Forwardable
-        forward :records, :each, :empty?, :size, :slice, :[], :to_a, :to_ary
+        delegate :each, :empty?, :size, :slice, :[], :to_a, :to_ary, to: :records
 
         include Base
 

elasticsearch-model/lib/elasticsearch/model/response/results.rb

@@ -10,8 +10,7 @@ class Results
         include Base
         include Enumerable
 
-        extend  Support::Forwardable
-        forward :results, :each, :empty?, :size, :slice, :[], :to_a, :to_ary
+        delegate :each, :empty?, :size, :slice, :[], :to_a, :to_ary, to: :results
 
         # @see Base#initialize
         #