reconhub/aweek: aweek version 0.3.0

This version of aweek introduces the flexible global week_start option, "aweek.week_start". This allows users to set the following line at the top of their scripts or in their .Rprofile to set the default start of the week:

aweek::set_week_start("Monday")

This is equivalent of setting options(aweek.week_start = 1L) and will have the side effect of setting the default week_start option for both date2week() and week2date(), making it easier to maintain scripts using aweek.