Implements support for 24-hour time if the relevant option is turned on.
Merge branch 'announcements': Adds a way to show announcements on upgrading the extension to a new version.
Merge branch '24h': Implements support for 24-hour time if the relevant option is turned on.
Switch the formats around: fix bug where setting the option to show 12-hr time was showing 24-hr time.
Show an in-app announcement when users upgrade to a version with 24-hour support.
Make the list more compact, by combining the map link with the address, and not displaying the calendar name for all-day events.

Fixes #192.
v1.4.3.0
Make version check accept upgrades across versions.

Instead of comparing equalTo new version, compare greaterThanOrEqualTo.
Add timestamps to log messages, disable logging by default.
Fix bug where if feeds.lastFetchedAt was null, calendars wouldn't update.
Clean up a few log statements.
Only show announcements when upgrading from a lower version.

So that every future upgrade doesn’t show the message over and over
again.
Log system info to the console.
Log feeds after parsing, and include number of events parsed.
Simplify error reporting, and include timezone offset info.
High DPI icons everywhere!
Maintain Low DPI versions of icons because the High DPI rasters look bad on a low DPI screen.
Remove too-frequent log message for refreshUI.
v1.4.4.0
Skip showing declined events in popup and for calculating time to next event.

Fixes #113.