0.5.0-beta

Database and ORM fixes and improvements, as well as InMemory storage for testing.

Changelog:

• Updated MySQL connection to work without the mysqlnd driver
• Implemented InMemory storage for unit tests; includes in-memory filtering,
  sorting, limiting etc
• Implemented many-to-many eager loading and counting
• Refactored, tested and fixed ORM relations and other ORM & database classes