Add support for not Active Record based factories

spec/factories_spec.rb

 require 'spec_helper'
 
-FactoryGirl.factories.map(&:name).each do |factory_name|
-  describe "#{factory_name} factory" do
-    it 'should be valid' do
-      expect(build(factory_name)).to be_valid
+describe 'factories' do
+  FactoryGirl.factories.each do |factory|
+    describe "#{factory.name} factory" do
+      let(:entity) { build(factory.name) }
+
+      it 'does not raise error when created 'do
+        expect { entity }.to_not raise_error
+      end
+
+      it 'should be valid', if: factory.build_class < ActiveRecord::Base do
+        expect(entity).to be_valid
+      end
     end
   end
 end