Fixed integration tests

refs https://github.com/TryGhost/Ghost/commit/b93e7d7f7c

Our CI wasn't running integration tests so this slipped through. When
adding a new table we must update the exporter to ensure it's exported,
and that means the tests need to be updated to check for it!

test/integration/exporter/exporter.test.js

@@ -50,6 +50,7 @@ describe('Exporter', function () {
                 'mobiledoc_revisions',
                 'oauth',
                 'offers',
+                'offer_redemptions',
                 'permissions',
                 'permissions_roles',
                 'permissions_users',