Filter out messages from self.

Closes #2.
Missing packet retransmission seems to work.

It turned out very difficult to test - I cannot
run test with just one instance of V8 because
unicast messages do not get delivered. However,
running test suite on my mac and in a Ubuntu VM
works - I'm guessing because they have different
IP addresses.

Because of this, I set one of the tests to be skipped,
since it'll just fail every time. Manual testing is
required for this one until I figure out how to
automate this properly.