Should handle Redis reconnection errors more gracefully

[rapala61]

BUG

Current Behavior

• Today, while Redis was being updated by Heroku. The Redis instance was inaccessible for a few minutes. This made G-Campaigns unable to connect. Throwing an ugly exception.

  2018-05-31T08:10:59.398388+00:00 app[web.10]: error: redisClient connection error: Error: Redis 
  connection to ec2-34-200-108-148.compute-1.amazonaws.com:10419 failed - connect 
  ECONNREFUSED 34.200.108.148:10419
  2018-05-31T08:10:59.400628+00:00 app[web.10]: /app/config/redis.js:21
  2018-05-31T08:10:59.400630+00:00 app[web.10]:       throw error;
  2018-05-31T08:10:59.400632+00:00 app[web.10]:       ^
  2018-05-31T08:10:59.400633+00:00 app[web.10]: 
  2018-05-31T08:10:59.400635+00:00 app[web.10]: Error: Redis connection to ec2-34-200-108-
  148.compute-1.amazonaws.com:10419 failed - connect ECONNREFUSED 34.200.108.148:10419
  2018-05-31T08:10:59.400636+00:00 app[web.10]:     at Object._errnoException (util.js:1022:11)
  2018-05-31T08:10:59.400637+00:00 app[web.10]:     at _exceptionWithHostPort (util.js:1044:20)
  2018-05-31T08:10:59.400639+00:00 app[web.10]:     at TCPConnectWrap.afterConnect [as 
  oncomplete] (net.js:1198:14)
  2018-05-31T08:11:00.092585+00:00 app[web.10]: info: Started worker 296
  

Desired Behavior

• Handle this disconnection more gracefully.

Steps to Replicate

• set the REDIS_URL with an invalid port