## Load a person, show that needs_loan == false
>> person = Person.find(18)
# ... snip ...
>> person.needs_loan
=> false

## Show that I can set needs_loan by hand and save
>> person.needs_loan = true
=> true
>> person.save!
=> true
>> person.needs_loan
=> true

## set it to false again
>> person.needs_loan = false
=> false
>> person.save!
=> true

## show that they are associated with an active loan
>> person.loan_requests.size
=> 4
>> person.loan_requests.any? { |l| l.active? }
=> true

## run the update_needs_loan! method to try to have the model set its
# own attribute to true
>> person.update_needs_loan!
=> true
>> person.needs_loan
=> false      #  It doesn't work.  What gives?