small refactor, replace WordTagFreq with Entry

dictionary.go

@@ -5,11 +5,16 @@ type Pair struct {
 	Flag string
 }
 
-type Token struct {
+type Entry struct {
 	*Pair
 	Freq float64
 }
 
-type DictLoader interface {
-	Add(*Token)
+func NewEntry() *Entry {
+	return &Entry{new(Pair), 0.0}
+}
+
+type Loader interface {
+	AddEntry(Entry)
+	CachePath(string) string
 }