Verify Arquillian can run on JDK 1.5

Setting compiler options target/source to 1.5 is not enough to verify that the code can actually run on JDK 1.5 since it ignores API changes. To avoid forcing developers to have JDK 1.5 installed to compile, we can add e.g. the Animal Sniffer Maven Plugin to verify using usage of JDK based on known api signatures.