Only update once, and wait upon reaching rate limit.

[calvinh99]

When rate limit reached, wait 15 minutes, then continue again.

Before running entire update loop, get the most recent update time -> most_recent_update

If you reach an artist who's last_updated time is after most_recent_update, then do not update because you already updated.

An artist who's last_updated time is before most_recent_update is an artist that has not been updated yet in the current execution.

[calvinh99]

Done