Update README.markdown for Achilles 3.0.2 release

Update README.markdown for Achilles 3.0.2 release
Fixes #55 Cannot find PersistenceManagerFactory for keyspace 'achilles_test' in test
Fixes #56 Test failed: EntityMetaTest.should_to_string
Support list of entities classes
Merge pull request #58 from serssp/listEntities

Support list of entities classes
Refactor slightly pull request