Allow for bot to pipe continous output back to channel

[ingardm]

For instance if we have a !ping -c5 github.com trigger you'd expect the output of the command to be returned line by line instead of waiting for the cmd to exit and then return all the output

[llimllib]

You could solve this right now by sending messages the way the github plugin does, but I agree that it's not a great answer. Will think about this for the future.

(Sorry for the ultra-slow response! I did read it and I will get to it. Eventually!)