Ping event should not trigger builds

While reviewing @bparees sample application I found out that he was triggering build with ping event, which is abiously wrong, I must have overlooked that case. So this PR extendeds integration tests with that test case and fixes it.
@bparees @mfojtik review pls.
Would it make sense for `Extract()` to return the default build itself instead of `nil`, so you could test `build == nil` instead of `!proceed`?