added suport for unix timestamp values on -start and -end parameters

pkg/util.go

@@ -1,13 +1,17 @@
 package main
 
 import (
+	"strconv"
 	"strings"
 	"time"
 )
 
 func parseInputTime(t string) (time.Time, error) {
 	//check if a negative duration.
 	var T time.Time
+	if i, err := strconv.ParseInt(t, 10, 32); err == nil {
+		return time.Unix(i, 0), nil
+	}
 	if strings.HasPrefix(t, "-") {
 		//parse as duration
 		dur, err := time.ParseDuration(t)