Add healthcheck

[jvperrin]

This would be nice to have so that the bot can be restarted automatically if it becomes unhealthy. We do need to make sure to avoid restarting over and over, but Marathon Kubernetes will rate-limit it a little bit so that it doesn't spam way too much, but that would not be very nice for people on IRC with all the joins/quits from bots.

This would also help with #8 so that if the bot crashes and can't reach Slack, then it would be restarted to avoid being down for a long time.

[dkess]

How do you envision the mechanics of this actually working?

[jvperrin]

Not sure yet, but I was loosely envisioning running a command that would check all threads (the bridge bot and all the IRC bots) are running, but the actual mechanics of how that would function are up for debate.

[cg505]

I think we might want to write a general way to interact with IRC that can be used both by slackbridge and ircbot. Then we can do something like connect to IRC, maybe send a message, and wait for a response. This could be in combination with a simple slack bot that just will just connect and send a message/wait for a response.
This is pretty complicated for a healthcheck though, idk

[dkess]

We can't use a message-based healthcheck because it would fill up Slack history