adding Util::Assert and tests

@drsnyder @pchojnacki 
implementation of guideline helpers described in https://github.com/Wikia/guidelines/pull/43. ```Assert:::boolean``` will log an error to Elasticsearch and hard fail when the checked boolean is false.
I think it would be good to leave a comment in here about why we are adding this-- that php's `assert` is not recommended but that we want a way to fail fast while enabling assertive programming?