Add smoke test to n-logger

[taktran]

Problems like #81, which stop logging from going to splunk completely don't get caught until someone notices splunk isn't logging.

@kitkat119 had a manual test which I modified in ./test.js. Hopefully quite straight forward to wire this up to be a proper smoke test that could run on circle ci.

Just need an api from Splunk to programmatically read back logs.

[rowanmanning]

This is fixed with the move to Heroku log drains I believe. We won't be adding any smoke tests to this library, more likely we'll be replacing it in future.