Introduce ioredis & msgpack

[behrad]

Redis persistence is compatible with ioredis, when requiring ioredis constructor in.
Options can be set via redisOptions

[mcollina]

I think we can just switch to ioredis, and remove the need for passing in the 'redis' module. This is a tiny breakage (will bump the major), but I think it's way better. We'll need to update the docs in mosca.

[behrad]

If you can do the merge & release today, I'm updating the PR.

[coveralls]

Coverage increased (+0.06%) to 91.478% when pulling 32d3663 on adpdigital:master into 135dce3 on mcollina:master.

[behrad]

This should not affect current deployments despite the configuration change.
All redis options are now passed flat to the ascoltatori.

[behrad]

Would you please check this @mcollina ? Fails seem not be related to this commit

[mcollina]

I have not much time to look into it. It seems some incompatibility somewhere in node v0.12 :(.
We can't drop that, unfortunately.

[behrad]

seems a microtime build error when building leveldown!!