Merge pull request #15 from melezov/master

Fixed History deserialization through history/snapshot delegates.
Mixin serialization test fixed.

Class can't be nested, since Jackson will fail in that case.
Removed custom jackson handler, since it seems new Jackson copes with it.
Doesn't jet work with Option[Mixin].

Use Revenj default credentials for DB access.
Fixed history test (now failing on update)