Update grpc dep to v1.0.4

[douglas-reid]

Trying to build a go_proto_library with_grpc, got:

undefined: grpc.SupportPackageIsVersion4

This was fixed by manually adding:

new_go_repository(
    name = "org_golang_google_grpc",
    commit = "8712952b7d646dbbbc6fb73a782174f3115060f3",
    importpath = "google.golang.org/grpc",
)

to my WORKSPACE.

I believe the issue is that https://github.com/pubref/rules_protobuf/blob/master/go/deps.bzl#L26 is set to "tag": "v1.0.2" (instead of "tag": "v1.0.4" as needed).

From: https://github.com/grpc/grpc-go/releases/tag/v1.0.4

Now the grpc support version is SupportPackageIsVersion4

[pcj]

Thanks @douglas-reid, required updating golang/protobuf as well as grpc/grpc-go for SupportPackageIsVersion4. Please re-open if you are still encountering issues. PR's also welcome in the future to get you in the contributors list.

[douglas-reid]

Many thanks, @pcj ! Switched to your latest commit and everything works.

You got to it before I could even get around to starting a PR to confirm the fix.