Ability to pass redis connection options

Update client to namespace calls, allow for eventEmitter registration and allow options to be passed to the redis client creation.
    
    * The namespace key was not being created correctly because this.key_prefix was being referenced by the function closure was being set as 'this' so the key prefix was being returned as null
    * Move for loop to capture the method name that is being operated on so we don't continualy reference zunionstore
    * The createClient should take opts call so we can pass through arbitrary options to the redis client creation.