Remove v1 code

internal/error.go

@@ -1,7 +0,0 @@
-package internal
-
-// Error is a custom error.
-type Error string
-
-// Error is an implementation of error interface.
-func (e Error) Error() string { return string(e) }

internal/proto.go

@@ -1,19 +0,0 @@
-package internal
-
-import "github.com/gogo/protobuf/proto"
-
-// Custom contains methods to satisfy proto.Message
-// including custom methods to satisfy protobuf for
-// non-proto defined types.
-type Custom interface {
-	Size() int
-	Empty() bool
-	Bytes() []byte
-	Marshal() ([]byte, error)
-	MarshalTo(data []byte) (int, error)
-	Unmarshal(data []byte) error
-	proto.Message
-
-	// Should contains for proto.Clone
-	proto.Merger
-}