Use redis for session management

[mjensenbitbucket-bot]

Warning: connect.session() MemoryStore is not designed for a production environment, as it will leak memory, and will not scale past a single process.

Upgrade the session store to use redis

[mjensenbitbucket-bot]

By default express-session uses MemoryStore which is known to have memory leaks and is not designed for production use.

https://github.com/expressjs/session