Fix for #102, show offending class if it is not found

With this change, output is

10:11:00 PIT >> INFO : SLAVE : 10:11:00 PIT >> WARNING : Could not load com.tonicsystems.jarjar.util.AntJarProcessorTest$7 (NoClassDefFoundError: com/tonicsystems/jarjar/util/AntJarProcessor)

10:11:00 PIT >> INFO : SLAVE : 10:11:00 PIT >> WARNING : Could not load com.tonicsystems.jarjar.util.AntJarProcessorTest$8 (NoClassDefFoundError: com/tonicsystems/jarjar/util/AntJarProcessor)

10:11:00 PIT >> INFO : SLAVE : 10:11:00 PIT >> WARNING : Could not load com.tonicsystems.jarjar.util.AntJarProcessorTest$9 (NoClassDefFoundError: com/tonicsystems/jarjar/util/AntJarProcessor)

10:11:00 PIT >> INFO : SLAVE : 10:11:00 PIT >> WARNING : Could not load com.tonicsystems.jarjar.util.JarTransformerTest$1 (NoClassDefFoundError: com/tonicsystems/jarjar/util/JarTransformer)

10:11:00 PIT >> INFO : SLAVE : 10:11:00 PIT >> WARNING : Could not load com.tonicsystems.jarjar.util.JarTransformerTest$2 (NoClassDefFoundError: com/tonicsystems/jarjar/util/JarTransformer)

so the culprit can be found and classpath fixed.