Fix up methods in Budget Class

- Fix up figureOutBudgetStartEndDate method in Budget class. The Budget
  start month and year should always be the current month and year. This
  way the logic implemented in the method will figure out on its own what
  should be they budget starting and ending dates.
- Move figureOutBudgetStartEndDate method to Budget Class as it is more
  appropriate for it to be there.
- fix up the getBudgetLength method in the Budget class to return the
  exact budget length value.