Change collect_ga_data to collect data for two days ago by default.

Since GA takes up to 24 hours to show collected data, we should run the
collect command after midnight to be able to collect data for every 
click from 24 hours ago. This means it should collect from two days ago
instead of yesterday.
Add 'today' as a valid date for the collect_ga_data command.

This will allow the dev server to collect data for the current day to
speed up testing.