Introduced Arquillian-based example for JPA 2.1 custom converter feature.

This project demonstrates following new additions to JPA 2.1
* Custom converter for `CreditCard` object which belongs to Employee
* JPA 2.1 schema generation / db seeding options (see `persistence.xml`)

In addition to Arquillian following tools has been used:
* AssertJ fluent assertions to verify the result of retrieving all objects from the datastore
* ShrinkWrap Maven resolve to bundle AssertJ with test deployment
Merge pull request #218 from bartoszmajsak/jpa-custom-converter

Introduced Arquillian-based example for JPA 2.1 custom converter feature