Adding default constructor to MockSerializationResult.

Just adding a default constructor to make easier to use it in unit tests.

Now we need use some like: `new MockSerializationResult(new JavassistProxifier(), cleanInstance(),
				new GsonBuilderWrapper(new MockInstanceImpl<>(jsonSerializers), new MockInstanceImpl<>(jsonDeserializers)));`
With this default constructor, we just use some like: `new MockSerializationResult();`

What do you think ?
Rollback this change. VRaptor is released, we cannot simply remove a class without bumping the major release version.