pkg: hide it by moving to _pkg.dev

The idea here is to preserve the history of `dev` branch development and its
code when merging with the `master`. Later this code could be moved into the
masters code where appropriate.

_pkg.dev/wire/payload/mgetdata_test.go

@@ -0,0 +1,19 @@
+package payload
+
+import (
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/wire/command"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetDataCommandType(t *testing.T) {
+	getData, err := NewGetDataMessage(InvTypeBlock)
+
+	assert.Equal(t, err, nil)
+	assert.Equal(t, command.GetData, getData.Command())
+}
+
+func TestOtherFunctions(t *testing.T) {
+	// Other capabilities are tested in the inherited struct
+}