Scraper missed an event when Metro changed the event time

[reginafcompton]

Summary
Recently, Metro changed the time of the "Finance, Budget, and Audit Committee" meeting on 3/14. The scraper did not acknowledge the change. Why? The EventLastModifiedUTC read as "2017-12-14T23:05:00.18" - in other words, the timestamp did not correspond with the time that Metro changed the event. As a result, the scraper did not scrape the event.

Brainstorming steps forward
(1) It seems possible that the Legistar EventLastModifiedUTC does not communicate the way our scrapers expect. As a result, we may need to limit the number of times we look for event updates. Once per hour seems reasonable.
(2) Does Metro have any control over this timestamp in the API? Can they insure that the timestamp changes when they update an event, or does Legistar fully automate this?

[reginafcompton]

Migrating to scraper opencivicdata/scrapers-us-municipal#239