Docker updates

[beforan]

• moved devbot dockerfile and source into a folder for the devbot container
  • we can now add more containers to this stack if needs be (e.g. redis)
• devbot dockerfile tidied up
  • all unnecessary environment variables removed #1
  • switched to alpine node image
• added docker-compose for dev and prod so we don't have to manually docker run and docker stop and everything else
• added Makefile for getting the image onto Docker Hub (or any registry really)
  • this needs doing for #12 as Rancher can't build, only pull
• added rancher-compose for use with Rancher #12