:s3_credentials will now accept a Pathname

Rails.root returns a Pathname and you can now declare your attachment
without having to call #to_s first:

has_attached_file :avatar,
                  :storage => :s3,
                  :s3_credentials => Rails.root.join('s3.yml')
(cherry picked from commit 65d7600b7246cb3bd8f10805fb618e5839694318)

lib/paperclip/storage.rb

@@ -232,7 +232,7 @@ module Paperclip
         case creds
         when File
           YAML::load(ERB.new(File.read(creds.path)).result)
-        when String
+        when String, Pathname
           YAML::load(ERB.new(File.read(creds)).result)
         when Hash
           creds

test/storage_test.rb

@@ -254,6 +254,28 @@ class StorageTest < Test::Unit::TestCase
     end
   end
 
+  context "with S3 credentials supplied as Pathname" do
+     setup do
+       ENV['S3_KEY']    = 'pathname_key'
+       ENV['S3_BUCKET'] = 'pathname_bucket'
+       ENV['S3_SECRET'] = 'pathname_secret'
+
+       rails_env('test')
+
+       rebuild_model :storage        => :s3,
+                     :s3_credentials => Pathname.new(File.join(File.dirname(__FILE__))).join("fixtures/s3.yml")
+
+       Dummy.delete_all
+       @dummy = Dummy.new
+     end
+
+     should "parse the credentials" do
+       assert_equal 'pathname_bucket', @dummy.avatar.bucket_name
+       assert_equal 'pathname_key', AWS::S3::Base.connection.options[:access_key_id]
+       assert_equal 'pathname_secret', AWS::S3::Base.connection.options[:secret_access_key]
+     end
+  end
+
   context "with S3 credentials in a YAML file" do
     setup do
       ENV['S3_KEY']    = 'env_key'