Log member joining.

Since Slack does not give us a way to retroactively see member join dates, it would be beneficial to keep a small logging that we can check up on.

[bcabio]

That can be done with the logger stuff that I'm doing. Do you want it to save to a file? Or to a DB?

Honestly I dont care either way. If we are storing user info into a DB, it would make sense to have a bit about each member's join time, so if that is easy enough, why not, but then again we dont have a DB set up yet so...

[arshbot]

I'm actually logging when members join in the analytics portion. And when members join individual channels as well

[bcabio]

I can just set up to be a file for now