[Feature] Ping-command.

[Johannestegner]

It would be great to be able to ping the bot in the channel it is available in to check if it runs or not.
This could be just as small a thing as writing ping <name-of-bot> with a pong response.

[ddworken]

In progress in #50 :)

Waiting to get a few other PRs in to minimize the rebase pain but should be in soon.