Improve UI a little bit

cmd/main.go

@@ -43,7 +43,7 @@ func main() {
 
 	for true {
 		cpustat := gupta.NewCPUStat(line, lineNew)
-		fmt.Printf("cpustat %.2f\n", cpustat.CPUUsage())
+		fmt.Printf("CPU usage %.2f%%\n", cpustat.CPUUsage())
 		time.Sleep(time.Duration(freq) * time.Second)
 		line = lineNew
 		lineNew = readProcStatLine()