Add birthday in new year in birthdays_of_this_week
Add birthday in new year in birthdays_of_this_week

Improve `User#birthdays_of_this_week` test to avoid that it fails again
by adding a case with a user born at the beginning of the year.

freakuency/agile-team-dashboard,freakuency/agile-team-dashboard,freakuency/agile-team-dashboard,freakuency/agile-team-dashboard