Fixed bug #31

This commit has two changes:
1. Fixed bug #31. [`collectInterfaces`](https://github.com/bennidi/mbassador/blob/master/src/main/java/net/engio/mbassy/common/ReflectionUtils.java#L69) needs to come first otherwise it pulls the interfaces from Object, except there are none. I also added a test case (`InterfaceTest`) and a `TestMessage3` class that actually uses an interface.
2. `SyncBusTest` didn't compile (there is no `net.engio.mbassy.events` package), I fixed the imports so that it did.