Add datadog surfacer

[manugarg]

This should be fairly straightforward. We should probably use:
https://github.com/DataDog/datadog-go

[manugarg]

Please let's know if this use is important to you and you'd like to see it implemented sooner.

[robpickerill]

Hey Manu, I'd like to also pick this up.

I suspect it will take me a few weeks to implement in between work and other commitments. I'll make a start here next week.

[manugarg]

Hey @robpickerill,

Sounds good. Thanks for picking it up. :)

[c6h12o6]

I accidentally picked this up (without talking to robpickeril, though I am a coworker of his). You can assign it to me if you'd like.

#594

[manugarg]

Closing this as it is done (#594, #627).