fix example.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

example/example.go

@@ -4,7 +4,7 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/gin-gonic/contrib/gzip"
+	"github.com/gin-contrib/gzip"
 	"gopkg.in/gin-gonic/gin.v1"
 )