tests for default.yaml

[breezykermo]

The default.yaml file (which is the configuration for frame when packaged as a Mac app) needs some basic tests, as some inconsistencies fail silently when running. These include:

• checking that no two events are named the same. The YAML loaded will just take the event furthest down the file if there are collisions.
• checking that all files in events exist on the filesystem. The non-existence of a video file will result in a fatal "frame error" at startup.
• checking that time strings are legitimate and return an actual object when converted to schedule events. We didn't realise that daily events (e.g. every().wednesday.at("17:00")) don't allow the specification of seconds, which led to unexpected behavior. Some badly interpreted strings don't seem to fail or crash frame, they just don't register the event.