Support offsets in token writer

Change-Id: I1a75f8b8b3e00a0d469580cb1abee72153bbe362
diff --git a/token_writer.go b/token_writer.go
index 3ddcf27..e1fabdf 100644
--- a/token_writer.go
+++ b/token_writer.go
@@ -31,8 +31,8 @@
 	tw.writer.Flush()
 }
 
-func (tw *TokenWriterSimple) Token(_ int, buf []rune) {
-	tw.writer.WriteString(string(buf))
+func (tw *TokenWriterSimple) Token(offset int, buf []rune) {
+	tw.writer.WriteString(string(buf[offset:]))
 	tw.writer.WriteRune('\n')
 }