Removed restriction on create for invoices with the same delivery date.

app/models/invoice.rb

@@ -25,7 +25,6 @@ class Invoice < ActiveRecord::Base
   belongs_to :order
 
   validates_presence_of :supplier_id
-  validates_uniqueness_of :date, :scope => [:supplier_id]
 
   named_scope :unpaid, :conditions => { :paid_on => nil }