udpated buildConfig

updated redis and fixed Spock dependencies
added customListener configuration field

added the possibility to add a custom worker listener in Config.groovy
added functionality to specify a custom worker and listener
increased version to 0.7 and updated README
fixed readme
fixed Readme again
moved test block back where it belongs
fixed a typo
Merge pull request #1 from peh/customListener

Custom WorkerImpl and WorkerListener