This PR begins to migrate Conduit to Linkerd2:
* The proxy has been completely removed from this repo, and is now located at
github.com/linkerd/linkerd2-proxy.
* A `Dockerfile-proxy` has been added to fetch the most-recently published proxy
binary from build.l5d.io.
* Proxy-specific protobuf bindings have been moved to
github.com/linkerd/linkerd2-proxy-api.
* All docker images now use the gcr.io/linkerd-io registry.
* `inject` now uses `LINKERD2_PROXY_` environment variables
* Go paths have been updated to reflect the new (future) repo location.
protobuf has a `go_package` option that can be used to explicitly name
Go packages such that they can be imported without additional rewrites.
This allows us to store proto files without additional, redundant
directories (which were used for packaging hints, previously).
This change adds an explicit `go_package` to all .proto files and
updates `bin/protoc-go.sh` to ensure these packages are output into
$GOPATH (so that the go_package can be absolute). This removes the need
to manually rewrite imports in bin/protoc-go.sh.
Kevin Lingerfelt
Oliver Gould