Add delete event
Updates after review
Merge branch 'subscription' of github.com:Metaswitch/clearwater-sas-resources into memcached_delete
Merge branch 'iss30' of github.com:Metaswitch/clearwater-sas-resources into memcached_delete
Merge branch 'master' of github.com:Metaswitch/clearwater-sas-resources into memcached_delete
Merge pull request #42 from Metaswitch/memcached_delete

[Reviewer: Matt] Add delete event