Bind Lambdas in :conditions

Let's say you want to find records based on the current time.

def find_within_last_week(*args)
  with_scope(:find => {:conditions => ['assignments.created_at > ?', 7.days.ago.to_s(:db)} do
    find(*args)
  end
end

Except, that time statement will be evaluated when the class is first loaded, which quickly makes it useless. The less-than-documented solution used to be

['assignments.created_at > ?', '#{7.days.ago.to_s(:db)']

But that's just silly when ruby has lambdas. With this patch, you can write:

def find_within_last_week(*args)
  with_scope(:find => {:conditions => ['assignments.created_at > ?', lambda {7.days.ago.to_s(:db)}} do
    find(*args)
  end
end