Channel.Alert gives success message now. Fixes #544.

This seems to work with my bot.

```
22:32:14 < Mikaela> alert ##Mkaysi again
22:32:14 < Yvzabevn> Alert to all ##Mkaysi ops: again (from Mikaela)
22:32:17 < Yvzabevn> OK.
22:32:29 < Mikaela> alert ##Mkaysi finally.
22:32:30 < Yvzabevn> Alert to all ##Mkaysi ops: finally. (from Mikaela)
22:32:32 < Yvzabevn> OK.
```