Updated deprecated hibernate configuration

Got the following warning:

    2014-09-16 12:21:15,255 [WARN] from org.hibernate.ejb.HibernatePersistence in play-internal-execution-context-1 - HHH015016: Encountered a deprecated javax.persistence.spi.PersistenceProvider [org.hibernate.ejb.HibernatePersistence]; use [org.hibernate.jpa.HibernatePersistenceProvider] instead.

Also see [the hibernate api docs](http://docs.jboss.org/hibernate/orm/4.3/javadocs/index.html?org/hibernate/ejb/HibernatePersistence.html).