About changing the codebase to Scala 2.10 based

[j5ik2o]

I'd like to use scala.concurrent.Future to implement Async Repository so change the codebase to Scala 2.10 based.

trait AsyncRepository {
// ...
  def resolve(id: Identity[ID], callback: Option[Future[E] => Unit] = None): Future[E]
// ...
}

http://docs.scala-lang.org/overviews/core/futures.html
http://docs.scala-lang.org/ja/overviews/core/futures.html