statsd cleanup

[dpep]

I was poking around and discovered the statsd subscriber. In addition to being excited to test it out in prod, I noticed a couple small improvements we might make to simplify - using the &. operator to guard against nil objects, and adding test coverage... what'd you think?

[jnunemaker]

Hey thanks!

Do you think we should warn or raise when the client is not set? I’m wondering if it would be confusing to have it fail silently.

[dpep]

yeah, if someone explicitly plugs in the statsd subscriber but doesn't provide a client, failing loudly makes sense to me. I just didn't want to change the functionality on my first pass...

we could also expose something in the config dsl that makes setup easier, eg.

Flipper.configure do |conf|
  conf.statsd = my_client
end