Minor fixes

• Fix NPE while adding new entity without ID (#3)
• Relax search methods in repositories (#5)

v0.2

• Add MindfulRepo#containsActive method and remove useles de/activate(entity)
• Fix package private API empty constuctors
• Enable Spring Repositories to track changes in added entities (em#persist usage)
• Cover Spring-based rpositories with tests
• Add UUID based Identifier implementation for convenience
• Minor API and Spring Repositories improvements

Initial release & publication

v0.1

Setup Bintray publication