Add validation on db parameter in adapter config

[bberry6]

When running "sails new", the socket.io-redis adapter config/sockets.js file has the value of "sails". If the user were to use this setting by simply uncommenting that line, then the subClient.select and the pubClient.select silently fail (the errors are not being monitored).

The only valid databases that redis has are indices 0 to 15. This pull request adds validation on the db parameter to prevent the silent failure.

[sgress454]

Thanks @bberry6, sorry I'm just finally getting around to this. First of all, thanks for pointing out the error in our default config file; I've patched that.

I'm hesitant to duplicate the Redis validation in our code, because it's not future-proofed. If a newer version of Redis allows database IDs > 16, or databases with string indexes, this would fail unnecessarily. But I definitely agree we should be doing something to indicate when the select command fails. At the very least we should display the error, but ideally we would wrap it in our own language since

{ [Error: ERR invalid DB index] command: 'SELECT', code: 'ERR' }

is not exactly a wealth of information (it doesn't even mention Redis).

If you'd like to take a crack at this I'd be happy to merge.

[mikermcneil]

@bberry6 @sgress454 can this error code be negotiated from redis? Best way to check is prbly to sniff it and log its _.keys(). If not, we should just inline this in this hook-- but the place to do that is the configure() function -- specifically by inserting these validations between what is currently lines 64 and 65

Thanks!

[mikermcneil]

@bberry6 to @sgress454's point, I'll follow up to open up this check so that it allows between 0 and 1000000, provided the number is an integer