Allow sending custom message

[AgrawalAmey]

knockknock can be a great general purpose library to send messages to different messaging clients. Why restrict it to just sending messages about training completion.

[AgrawalAmey]

I am creating a PR for the same.

[armstrys]

Love how easy KnockKnock is to use and I second this request! I am using this for large data processing projects and while it's not a big deal that it refers to everything as "training" it would be hugely helpful to be able to add a label by project so that I can more easily track which jobs are running/finished/crashed.

[AgrawalAmey]

#62

[alanhoyle]

I came looking for a generic notifier library, and KnockKnock is so close! I also wish it could take the notification message as a parameter.

One imagines it wouldn't be that difficult to add a parameter....