Create docker image or dockerfile

[ptman]

I think I've seen people request this several times.

Here's some scattered info:

• revel/revel#845
• revel/cli#1
• https://github.com/notzippy/FrameworkBenchmarks/tree/master/frameworks/Go/revel
• https://github.com/revel/revel/wiki/Roadmap
• https://jbeckwith.com/2015/05/08/docker-revel-appengine/