don't save a subreddit if it doesn't exist (URL is a search page)
don't save data when in incognito, per google guidelines
be able to remove select subreddits from list
be able to clear data
make options page nicer
reset the counts on a schedule (weekly?), but keep the subreddit listed
so that new subreddits can surpass old subreddits if they're visited a lot.
Or do exponentially weighted moving average stuff instead.
remove alerts for production
make sure filter doesn't filter out perfect matches
ask for user confirmation in options before deleting all subreddits