Fix failing tests

[mhchia]

This PR should fix https://github.com/mhchia/sharding-p2p-poc/issues/2, and the tests listed below

• TestRouting
  • It seems the reason for it to fail is that dht queries fail. I ran the tests in libp2p/go-libp2p-kad-dht and found them failed as well. So further I tried gx-go rw to make the tests depend on versioned dependencies, and then the tests in libp2p/go-libp2p-kad-dht succeeded. Therefore, I tried it in our repo and it works, but for unknown reason.
    • Just a note that the dht failed because of dht: error writing message, trying again: proto: invalid UTF-8 string dht_net.go:271. It seems the proto data contained invalid UTF-8 in the field Key.
  • Use gx to manage dependencies
• TestPubSubNotifyListeningShards
  • Uncomment n.PublishListeningShards

[mhchia]

Note: Consider using other dependency management tools like Bazel, inspired by https://github.com/prysmaticlabs/prysm