Copy codes and status from grpc project

This copies the codes and status package from grpc as it is the only references
to the grpc project from ttrpc. This will help ensure that API breaking changes
in grpc do not affect ttrpc.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

client.go

@@ -26,11 +26,11 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/containerd/ttrpc/codes"
+	"github.com/containerd/ttrpc/status"
 	"github.com/gogo/protobuf/proto"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 )
 
 // ErrClosed is returned by client methods when the underlying connection is