#98 Warn when sending memos to nicks that have never joined

person: tell freedomlover I hope you get this message!
funbot: person, your memo for freedomlover has been saved.

fr33domlover joins

person:       Hey fr33domlover, did you get my message?
fr33domlover: No, I didn't :(
person:       Huh, funbot said it was saved…
fr33domlover: Who did you send it to?
person:       You, freedomlover!
fr33domlover: Ah, I'm actually `fr33domlover`, not `freedomlover`
person:       Ohh. Hmm. I wish funbot had warned me…

## Earlier person: tell freedomlover I hope you get this message! funbot: person, your memo for freedomlover has been saved. ## Later fr33domlover joins person: Hey fr33domlover, did you get my message? fr33domlover: No, I didn't :( person: Huh, funbot said it was saved… fr33domlover: Who did you send it to? person: You, freedomlover! fr33domlover: Ah, I'm actually `fr33domlover`, not `freedomlover` person: Ohh. Hmm. I wish funbot had warned me… ## Solution - funbot should keep track of which nicks have joined the channel - If you try to send a memo to someone who has never joined, funbot should give a warning (or error, and refuse to send?) - Optional upgrade: Instead of "someone who never joined", use, "someone who hasn't been in the channel in the last [month]", and throw away information about nicks that's been around longer than that.