Upgrade to Akka 2.3.0-RC4
Prepare JournalSpec for being moved to another project
Start using akka-persistence-testkit
Several upgrades

- akka 2.3.0
- akka-persistence-testkit 0.2
- cassandra-driver-core 2.0.0-rc3
Set development version to 0.3-SNAPSHOT
Merge branch 'master' of github.com:krasserm/akka-persistence-cassandra into mastersthesis