Delete all Rails code

We're going to start fresh.
Set files to ignore for Go

Taken from:
https://github.com/github/gitignore/blob/8a28b1c4c67272aa4efc6f5e5eb77c205449427d/Go.gitignore
Create a minimum-viable Go project

This project has a single passing test (1=1 equality) to show that the
test suite is working as expected.

We're using Gom for project dependencies because it allows
dependencies to be vendored easily into the project and doesn't
require the repo to be checked out on the `$GOPATH`. This conforms to
how some development teams expect to work in terms of where they check
their code out.

We're using `make` as the build tool to make the vendor process easier
for testing the project itself.
Add a working HTTP server with a /healthcheck endpoint

The `/healthcheck` endpoint is what we'll use to monitor this service
from. It's here to show that the application in question is working.
Allow setting the HTTP port using an environment variable
Log requests using JSON

We want to be friendly to our current logstash/kibana setup.
Test the /healthcheck endpoint using the top-level http muxer
Run the tests as the default task for Jenkins
Merge pull request #3 from alphagov/convert-to-go-app

Convert to go app
Add logrus dependencies

This gets the build green again as these dependencies weren't defined
beforehand.