remove httmock

as it causes tests to hang outside of the dev vm
Simplify the status endpoint and return status

If one of our deps isn't ok then we should be sending a 5xx status.

There was a lot of dupe between the two status checks so I've pulled it
out into a function.

The status of the admin app is now dependant on the status of its
dependencies.
Merge pull request #35 from alphagov/no-httmock

remove httmock
Merge pull request #36 from alphagov/improve-status-endpoint

Simplify the status endpoint and return status