The example utilizes native bazel rules (proto_library, cc_proto_library,
java_proto_library, java_lite_proto_library) to show how easy it is to
build protobuf with bazel's native support. It also makes use of well
known types which was not possible until the latest bazel 0.5.4 release
and https://github.com/google/protobuf/pull/3594 .