Weekly with interval skips the first day if on: is Sunday

[d4rky-pl]

There's a bug in next_in_recurrence method of Event::Weekly:

      private def next_in_recurrence
        return @date if !initialized? && @options[:on].include?(@date.wday)

        if (next_day = @options[:on].find {|day| day > @date.wday })
          to_add = next_day - @date.wday
        else
          to_add = (7 - @date.wday)                # Move to next week
          to_add += (@options[:interval] - 1) * 7  # Add extra intervals
          to_add += @options[:on].first            # Go to first required day
        end

        new_date = @date.to_date + to_add
        @options[:handler].call(new_date.day, new_date.month, new_date.year)
      end

If @options[:on] is set to Sunday it gets converted to 0 which breaks the check in the if conditional. This in turn causes the code to skip to the else branch and miss one day.

The fix is to map Sunday to be 7 instead of 0, therefore making sure it's compared correctly and no day is skipped:

next_day = @options[:on].map { |day| day == 0 ? 7 : day }.find {|day| day > @date.wday }

I can prep a PR if this gem is still maintained but I saw after last time there was still no release (#40)