Update deprecated package

At http://speter.net/ it says that the speter.net/go/exp/math/dec/inf has been replaced by gopkg.in/inf.v0

helpers.go

@@ -10,7 +10,7 @@ import (
 	"strings"
 	"time"
 
-	"speter.net/go/exp/math/dec/inf"
+	"gopkg.in/inf.v0"
 )
 
 type RowData struct {