Support offsets in token writer

Change-Id: I1a75f8b8b3e00a0d469580cb1abee72153bbe362
diff --git a/matrix.go b/matrix.go
index 98fc32c..545cd07 100644
--- a/matrix.go
+++ b/matrix.go
@@ -493,7 +493,7 @@
 				if DEBUG {
 					fmt.Println("-> Flush buffer: [", string(buffer[bufft:buffc]), "]", showBufferNew(buffer, bufft, buffc, buffi))
 				}
-				w.Token(0, buffer[bufft:buffc])
+				w.Token(bufft, buffer[:buffc])
 				rewindBuffer = true
 				sentenceEnd = false
 				textEnd = false