Fixed two small bugs: misnaming of check_download_file() at import,
and then calling that file with util. as prefix.
Rewrote lyra_event_list() to work with LYRALightCurve only able to
take in one date as input at a time.
Added kwarg to lyra_event_list() to return time and flux as well.

Also changed start_time and end_time inputs to start_date and end_date.