Migrate from FEST 2 to AssertJ

The migation guide at http://joel-costigliola.github.io/assertj/assertj-core-migrating-from-fest.html
described all necessary steps to migrate from FEST 2.x to AssertJ 1.6.0.

In the future [assertj-joda-time](http://joel-costigliola.github.io/assertj/assertj-joda-time.html) and
[assertj-guava](http://joel-costigliola.github.io/assertj/assertj-guava.html) might also come in handy
for writing more concise tests for Dropwizard (which is using both, JodaTime and Google Guava).