Iss 57 implement RANDOMKEY command

[osteensco]

addresses #57

• adds randomkey command, Randomkey field to HandlerFuncParams, and randomKey method to keyspace
• adds Randomkey method to generic api

while my tests pass, I'm not 100% sure if adding a method to echovault/keyspace.go was the ideal approach so let me know if I need to adjust anything.

[kelvinmwinuka]

Hi @osteensco

This is a great PR! I like the approach of adding a randomKey method to keyspace. That's the approach I would've gone for as well.

I made a slight change to your PR. For the RANDOMKEY test, I set up some keys before executing the test. Initially, the test relied on the keys set up by other tests. The problem with this is that it makes the test flaky. Due to the test running in parallel to the other tests in the suite, there's no guarantee that the RANDOMKEY test will run after the other tests. This was leading to an issue where the RANDOMKEY test would periodically fail when no keys were found.

Other than that, it looks good, and I will approve it.