Rename flag frequency to interval

This is actually a more accurate description of the functionality.

cmd/main.go

@@ -25,8 +25,7 @@ func main() {
 	var partition, netInterface string
 	var load, memory, cpu bool
 
-	flag.IntVar(&freq, "frequency", 5, "Frequency of polling in secods")
-	flag.IntVar(&freq, "f", 5, "Frequency of polling in secods")
+	flag.IntVar(&freq, "i", 5, "polling inteval")
 	flag.BoolVar(&memory, "m", false, "Poll memory")
 	flag.BoolVar(&load, "l", false, "Poll load")
 	flag.BoolVar(&cpu, "c", false, "poll CPU usage")