Remove pkg/errors; Update Gopkg.toml, but not GRPC because it breaks.

client/grpc_client.go

@@ -6,7 +6,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/pkg/errors"
 	context "golang.org/x/net/context"
 	grpc "google.golang.org/grpc"
 
@@ -105,7 +104,7 @@ func (cli *grpcClient) StopForError(err error) {
 func (cli *grpcClient) Error() error {
 	cli.mtx.Lock()
 	defer cli.mtx.Unlock()
-	return errors.Wrap(cli.err, "grpc client error")
+	return cli.err
 }
 
 // Set listener for all responses