Addresses #66.
Addresses #67.
* Update test-infra to use the default build/unit test runners, which includes building go code and linting markdown files.
* Remove the integration tests, as they only start Knative Serving, which is irrelevant for this repo.
Bonuses:
* fix unbuildable `grpc-ping-go` sample
* remove test-infra import hack from `Gopack.lock` and `update-deps.sh`
Adriano Cunha