moved license to root, more tests
added abilitity to obtain a direct ref to the model
added support for persistence modes

Journaling (default), manual snapshots and snapshot per transaction
adding tests, doc comments and test refactoring
added Command.Now as DateTime.Now substitute
Custom IFormatter allowed for one time snapshots

Added optional IFormatter parameter to Engine.WriteSnapshotToStream()
added tests, refactoring
api redesign + refactoring of proxy attributes
refactoring proxy attribs, DateTime.Now surrogate