0.2.0 Move Transaction to thesis/transaction

Added

• Add Persister\InMemory for testing.
• Add UnitOfWork::close() method.

Changed

• BC Break: Thesis\ORM\Transaction moved to Thesis\Transaction in a separate thesis/transaction package.
• BC Break: Flip order of Flip $class and $persister parameters in Repository::__construct() and UnitOfWork::repository().

Fixed

• UnitOfWork is now always closed.