Add support for Drone

[mwildehahn]

I was initially going to go with Conveyor, but wanted more flexibility in building frontend assets (ie. pushing to a cloudfront distribution) and I didn't want that all being done within a Dockerfile.

This basically is just a repurposed version of the Conveyor stack.

[phobologic]

Closing this too - my guess is you won't be getting back to it anytime soon, @mhahn - if you do, go ahead and re-open.