Allow nil for #per, to return records without limit

lib/kaminari/models/page_scope_methods.rb

@@ -3,7 +3,9 @@ module Kaminari
     # Specify the <tt>per_page</tt> value for the preceding <tt>page</tt> scope
     #   Model.page(3).per(10)
     def per(num)
-      if (n = num.to_i) <= 0
+      if num.nil?
+        limit(nil)
+      elsif (n = num.to_i) <= 0
         self
       elsif max_per_page && max_per_page < n
         limit(max_per_page).offset(offset_value / limit_value * max_per_page)

spec/models/active_record/scopes_spec.rb

@@ -58,6 +58,11 @@ if defined? ActiveRecord
             it { should have(5).users }
             its('first.name') { should == 'user001' }
           end
+          
+          context "page 1 per nil" do
+            subject { model_class.page(1).per(nil) }
+            it { should have(model_class.count).users }
+          end
         end
 
         describe '#padding' do