Add basic test for the AllocationTrackerClassFileTransformer

This PR adds a very basic test for the ```AllocationTrackerClassFileTransformer```. It checks
- whether classes from the tracker packer are ignored
- whether classes with the wrong prefix are ignored
- whether the byte representation of classes are changed by the transformer
maybe we should start with ```assertThat(actual.length, is(greaterThan(byteArray.length)));``` and see what we come up with later ;-)