Move factory associations logic to evaluator_class

evaluator_class contains the fully-inherited list of attributes; this
includes parent classes, traits, etc. When calculating associations for
an individual factory, the factory should use inheritance to build the
list instead of merely accessing association attributes on itself.

Closes #293

lib/factory_girl/factory.rb

@@ -53,7 +53,7 @@ def human_names
     end
 
     def associations
-      parent.associations + attributes.associations
+      evaluator_class.attribute_list.associations
     end
 
     # Names for this factory, including aliases.

lib/factory_girl/null_factory.rb

@@ -7,7 +7,6 @@ def initialize
     end
 
     delegate :defined_traits, :callbacks, :attributes, :constructor, :to => :definition
-    delegate :associations, :to => :attributes
 
     def compile; end
     def class_name; end

spec/factory_girl/null_factory_spec.rb

@@ -5,12 +5,10 @@
   it { should delegate(:callbacks).to(:definition) }
   it { should delegate(:attributes).to(:definition) }
   it { should delegate(:constructor).to(:definition) }
-  it { should delegate(:associations).to(:attributes) }
 
   its(:compile)          { should be_nil }
   its(:class_name)       { should be_nil }
   its(:default_strategy) { should == :create }
   its(:attributes)       { should be_an_instance_of(FactoryGirl::AttributeList) }
-  its(:associations)     { should be_empty }
   its(:evaluator_class)  { should == FactoryGirl::Evaluator }
 end