Explicit support of redisClient({ url })

[thom4parisot]

Merging this would require to alter the content of https://github.com/mcollina/mosca/wiki/Mosca-advanced-usage.

fixes #571

[mcollina]

that will work for the persistence, you might need to do the same for https://github.com/mcollina/ascoltatori

[thom4parisot]

@mcollina ah gotcha, I thought they were sharing the same logic and now I understand better the naming of the config object :-) Will do and follow up on this issue. Thanks for your help!

[mcollina]

Merging this in the meanwhile!