Fixed
* Made trailscraper timezone-aware. Until now, trailscraper implicitly treated everything as UTC, meaning relative timestamps (e.g. `now`, `two hours ago`) didn't work properly when filtering logfiles to download or records to generate from. (39)
Added
* New command `trailscraper last-event-timestamp` to get the last known event timestamp.
* New flag `trailscraper download --wait` to wait until events for the specified timeframe are found.
Useful if you are waiting for CloudTrail to ship logs for a recent operation.