Have InMemoryTracker log.debug metrics for easy debugging.

I've seen literally 3 separate developers in the last 2 weeks add a "log to CW + also log.debug" helper methods.

But then, in one case, we ended up taking the log.debugs out, as it was too chatty in production.

Seems like InMemoryMetricTracker always logging would be a good balance of "useful for development but no affect on production".