Support notification to multiple channels

[mboldt]

We have a use case where we want a couple of individuals to receive slack notifications in their @user channels, but don't want to manage multiple puts as this is repeated throughout our pipeline at failure steps. It seems simple enough to add a for loop over whitespace-separated channels in out. I'm happy to take a shot at this and submit a PR if there's interest.

[jhunt]

Sounds good to me, go ahead and take a crack at it :)

[mboldt]

I submitted a PR #20 and would love to see it merged. Anything I can do to help?

[lnguyen]

new release cut @mboldt

[mboldt]

Awesome; thank you!