First pass at dockerizing.
This dockerfile builds correctly, and runs locally.  TODO: Pass ENV better.
Hardcode port for now.
If we have nil URI, we should fall back to using a relative URL for this server.
Add some documentation about running locally and on AWS.  [#82679046]

https://www.pivotaltracker.com/story/show/82679046
Add documentation for launching using Fig.
Use Protocol relative urls in demo directory
Have fig mount and use the local filesystem for development work.
Ignore cache folder, eleasticbeanstalk folder.
Configure unicorn worker count by ENV.
Update to ruby 2.1.5 for Copy on write forking in unicorn.