add webmock gem
switch specs to use webmock
encapsulate Users within Client
convert to using webmock instead of stubs
removing unnecessary dummy client methods

dummy client no longer used in 'support' app tests, just
in development mode, so it can be really stripped down to its
bare minimum
bump zendesk_api gem to 1.0.1

this is to generally stay up to date with the gem,
and to stop using a release candidate version
Merge pull request #10 from alphagov/use-webmock-instead-of-double-for-testing

Use webmock instead of test double for testing