Add vendor

Specifically because I want to modify a dependency

vendor/github.com/mattn/go-localereader/localereader.go

@@ -0,0 +1,19 @@
+package localereader
+
+import (
+	"bytes"
+	"io"
+)
+
+func NewReader(r io.Reader) io.Reader {
+	return newReader(r)
+}
+
+func UTF8(b []byte) ([]byte, error) {
+	var buf bytes.Buffer
+	n, err := io.Copy(&buf, newReader(bytes.NewReader(b)))
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes()[:n], nil
+}