Use idiomatic ruby for User#hours_entered_for_day
REFACTORED User#expected_hours

Decomposed expeted_hours into:
  work_days_between_dates(start,finish)
  first_scheduled_date_in_future?(date)
  never_worked?
  first_scheduled_date

  The code is negibly less performant but much more expressive. This
  can be refactored into a UserWorkload class along with
  User#target_hours_offset(date). As a bonus we now have an ability
  to add logic for holidays in User#work_days_between_dates
Merge pull request #30 from xn/user_refactor

User refactor