Introduce EOT (end-of-transmission) marker

Change-Id: I7946e95c80fd7cd6ac1e0dd2fe5b188105f30534
diff --git a/token_writer.go b/token_writer.go
index a10f112..3ddcf27 100644
--- a/token_writer.go
+++ b/token_writer.go
@@ -6,7 +6,8 @@
 )
 
 type TokenWriterI interface {
-	SentenceEnd()
+	SentenceEnd(int)
+	TextEnd(int)
 	Token(int, []rune)
 	Flush() error
 }
@@ -21,10 +22,15 @@
 	return &TokenWriterSimple{bufio.NewWriter(w)}
 }
 
-func (tw *TokenWriterSimple) SentenceEnd() {
+func (tw *TokenWriterSimple) SentenceEnd(_ int) {
 	tw.writer.WriteRune('\n')
 }
 
+func (tw *TokenWriterSimple) TextEnd(_ int) {
+	tw.writer.WriteRune('\n')
+	tw.writer.Flush()
+}
+
 func (tw *TokenWriterSimple) Token(_ int, buf []rune) {
 	tw.writer.WriteString(string(buf))
 	tw.writer.WriteRune('\n')