Add redis database and nawak-redis test

[idlewan]

Redis is a fast in-memory database.
While it won't be applicable to huge databases that don't fit in memory, having redis tests is still quite useful to determine if its use can add or substract performance compared to a postgresql or mysql setup with prepared queries.

[idlewan]

Rebased on #902 to be able to very cleanly select either the redis or postgresql database backend while reusing all the common code.

[aschneider-techempower]

I have a feeling that there's some issue with configuration somewhere.

Output Error.

While you are at it, please rebase on master.

[idlewan]

Rebased on master.

I'm guessing that redis wasn't running, I put in a fix.

[aschneider-techempower]

Error and Output

I've checked the redis connectivity with redis-cli and it appears to have information in there, so that's not the issue.

[idlewan]

The error (Error: unhandled exception: Connection refused [EOS]) is the program quitting right after startup because it can't connect to redis.
Maybe the database hostname isn't replaced right. Could you please post the beginning of the file model_redis.nim (I'm interested in the db = open(...) line), that should have been modified after the replace_text in setup_redis.py has run?

[aschneider-techempower]

You're right

I fixed the host manually and it appears that you failed the fortunes test.

You can check out the requirements here

We can merge it as is if you like, with fortunes commented out, or you can fix the fortunes and update the PR (also fix the string substitution if possible)

[idlewan]

That should do it.