Break compatibility with Go 1.3

This is essentially a revert of c4178e5.

Author: mibk

suffixtree/suffixtree.go

@@ -41,7 +41,7 @@ func New() *STree {
 // Update refreshes the suffix tree to by new data.
 func (t *STree) Update(data ...Token) {
 	t.data = append(t.data, data...)
-	for _ = range data {
+	for range data {
 		t.update()
 		t.s, t.start = t.canonize(t.s, t.start, t.end)
 		t.end++