Easy older go compat

`go range` without loop values is new to 1.4. some of us are stuck with older go (wheezy backport is 1.3.3)
merge if you wish - this was a quick one

bot.go

@@ -38,7 +38,7 @@ func (b Bot) Listen(subscription chan<- Message, interval time.Duration) {
 	latestUpdate := 0
 
 	go func() {
-		for range pulse.C {
+		for _ = range pulse.C {
 			go getUpdates(b.Token,
 				latestUpdate+1,
 				updates)