pass redis options through, rather than attempt to parse them

[alex-h-strachan]

Use case - I would like to use a redis configuration like
{ url: 'my-connection-url', tls: { servername: 'my-servername' } }

This is the easiest configuration for Microsoft Azure's fully managed redis. While it's possible to support this with the existing configuration it requires de-structuring the connection url, passing it through to Kue where it will be re-constructed and passed back. With this PR, the same opts can be provided to the redis.createClient() function as go to Kue.

To maintain compatibility, I've translated the options.redis.socket to the "path" argument passed to redis & I took the options.redis.options and spread them into the main configuration, so they should still be supported.