Dockerize iHat

REFERENCES
===
https://www.pivotaltracker.com/story/show/82965638

See the readme on the branch for installation instructions:

https://github.com/Tahi-project/iHat/blob/dockerize/README.md

TODO:

- [x] [Open URL on successful boot](https://github.com/Tahi-project/ihat/pull/27#discussion_r21470287)
The ENV variables in this context followed by a colon means "pass through these environment variables" from your environment into docker

To verify, run:
```console
source .env.development
fig run web env 
```