using Java 1.6 to be compatbible with older environments, 1.7 not really needed anyways
hotfix for classpath probles (method not found if e.g. google.common and guava are in cp)
moving de.javagil.columbo to de.javagil.columbo.core as preparation of adding de.javagil.columbo.annotations and de.javagil.columbo.assertions