add like structure

spec/acceptance/learning_objects_spec.rb

@@ -33,4 +33,16 @@ resource 'Learning Objects' do
     end
   end
 
+  post '/v1/learning_objects/:id/like' do
+    let(:id) { learning_objects.first.id }
+
+    example 'Liking a learning object' do
+      likes = learning_objects.first.likes
+      do_request
+      expect(path).to eq("/v1/learning_objects/#{id}/like")
+      expect(JSON.parse(response_body)).to eq(likes + 1)
+      expect(status).to eq(200)
+    end
+  end
+
 end