Add a centralized logging service

[sabaimran]

requirements

• logs all info, debug, and error logs
• centralizes them in a query-able format
• allows us to add alerts

after a bit of investigation, I've settled on using this cloudwatch handler library for pushing logs to AWS - Cloudwatch. see code changes in e2a47d2.

I explored Mezmo/LogDNA, but found the onboarding experience difficult to understand -- see logdna/python#109. DataDog is too expensive, NewRelic was too invasive, and Sentry is limited outside of error/reporting.