Add failing spec

Ref: #142

spec/chrono_model/time_machine/as_of_spec.rb

@@ -106,6 +106,8 @@
       it { expect(Foo.as_of($t.foo.ts[1]).includes(:bars).first.bars).to eq [] }
       it { expect(Foo.as_of($t.foo.ts[2]).includes(:bars).first.bars).to eq [$t.bar] }
 
+      it { expect(Foo.as_of($t.foo.ts[0]).includes(:goo).first).to eq $t.foo }
+
       it { expect(Foo.as_of($t.bar.ts[0]).includes(:bars).first.bars.first.name).to eq 'bar' }
       it { expect(Foo.as_of($t.bar.ts[1]).includes(:bars).first.bars.first.name).to eq 'foo bar' }
       it { expect(Foo.as_of($t.bar.ts[2]).includes(:bars).first.bars.first.name).to eq 'bar bar' }

spec/support/time_machine/structure.rb

@@ -22,13 +22,22 @@ module ChronoTest::TimeMachine
   adapter.create_table 'foos', :temporal => true do |t|
     t.string     :name
     t.integer    :fooity
+    t.references :goo
   end
 
   class ::Foo < ActiveRecord::Base
     include ChronoModel::TimeMachine
 
     has_many :bars
     has_many :sub_bars, :through => :bars
+
+    belongs_to :goo, class_name: 'FooGoo', optional: true
+  end
+
+  class ::FooGoo < ActiveRecord::Base
+    include ChronoModel::TimeGate
+
+    has_many :foos, inverse_of: :goo
   end
 
   class ::Boo < ActiveRecord::Base
@@ -61,6 +70,10 @@ class ::Moo < ActiveRecord::Base
     t.references :boo
   end
 
+  adapter.create_table 'foo_goos' do |t|
+    t.string :name
+  end
+
 
   class ::Bar < ActiveRecord::Base
     include ChronoModel::TimeMachine