Log levels should be more granular

[rmerrill-fw]

The majority of log messages are at level info. If I set the log level to notice I get no log messages at all, but if I set it to info I get a log message for every single redis transaction.

I really just want to log significant events like disconnect and reconnect attempts.

[anarthal]

Hi! This is actually fixed in the upcoming 1.91 release. We're now using

• Error when there is a communication error with the server, like a connection establishment error or a ping timeout.
• Info for successful connection attempts. This is specially useful if you work with Sentinel, aa it logs the details of the concrete instance that oa being contacted.
• Debug for everything else. In particular, the "xyz bytes written" message now uses debug.

PR to look at is #389.

Let me know if it looks good to you.

Cheers,
Rubén.