DevVM now lives in pp-puppet

We've moved the dev vm and this replicate script was still referencing
the old location. It now needs to explicitly say development-1 as there
are multiple VMs attached to that Vagrantfile.
Add deprecation warning for write API by name

We "deprecated" using the `/data-set-name` URL some time ago in favour
of `/data-group/data-type`. This is the first step towards actually
deprecating it - make some noise about it now.
Merge pull request #273 from alphagov/fix-replicate-db

DevVM now lives in pp-puppet
Merge pull request #274 from alphagov/add-deprecation-warning

Add deprecation warning for write API by name
Use abort() for error handling

This will make it easier to refactor common code when we implement the
data-set emptying endpoint.

Also modify exception handler to extract the description from the
HTTPError, rather than the name
Refactor the way POSTs are validated and handled

- split validation of data-set existence and authorization into two
  helpers
- rename _write_to_data_set to _append_to_data_set due to the fact that
  it's called by a POST, and we will implement a "set" (PUT) later.
- change signature of _append_to_data_set to take data as an argument,
  rather than the function extracting it from the global request object
  (side effect, meh)
Capitalize HTTP verbs POST, DELETE
Add tests for PUT to data-set with empty JSON list

- To implement "clear the data-set" we're allowing the user to HTTP PUT
  an empty JSON list, which overwrites the contents of the data set.
- We currently *only* allow an empty JSON list - return an error
  otherwise.
Make behave tests use data group/type URLs

Rather than testing the /data-set-name endpoint (which is deprecated)
we're now testing using the /data/data-group/data-type endpoint.
SQUASH into tests
WIP Implement PUT method for empty JSON list