This updates tests to use latest rails 5 practice
and updates ALL dependencies that could be updated
Performance testing shows that performance has not regressed
if anything it is marginally faster now.
Instead of adding email to unsubscribe url store it in redis for 1 hour
rate limit calls to unsubscribe endpoint to ensure there is no risk of
bloating redis
Also move controller to request specs
Guo Xiang Tan
Sam
OsamaSayegh
Arpit Jalan