Allow wildcard purging

- This should give us the ability to do things like
    `curl -X PURGE /data/.*`
    `curl -X PURGE /data/data-group/.*`
    `curl -X PURGE /data/data-group/type*`
Add std-out logging

- Hopefully this will add a bit more immediate visibility to what we're purging when running fabric commands/hitting varnish with cURL requests
Change 405 to 401

- I think this is correct, you're not not authorized (401) to purge from outside the access control list
Change 401 to 403

- 401 should give some explanation of why the request failed (http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html) and allow it to retry, whereas 403 should not, and will not retry.
Merge pull request #379 from alphagov/wildcard_purging

Wildcard purging