Rewind tempfiles after get saved to storages

Re-fix of #838, #766, #911

lib/paperclip/storage/fog.rb

@@ -90,6 +90,8 @@ def flush_writes
             retried = true
             directory.save
             retry
+          ensure
+            file.rewind
           end
         end
 

lib/paperclip/storage/s3.rb

@@ -310,6 +310,8 @@ def flush_writes #:nodoc:
           rescue AWS::S3::Errors::NoSuchBucket => e
             create_bucket
             retry
+          ensure
+            file.rewind
           end
         end
 

test/storage/fog_test.rb

@@ -111,6 +111,12 @@ class FogTest < Test::Unit::TestCase
         directory.destroy
       end
 
+      should "be rewinded after flush_writes" do
+        files = @dummy.avatar.queued_for_write.map{ |style, file| file }
+        @dummy.save
+        assert files.none?(&:eof?), "Expect all the files to be rewinded."
+      end
+
       should "pass the content type to the Fog::Storage::AWS::Files instance" do
         Fog::Storage::AWS::Files.any_instance.expects(:create).with do |hash|
           hash[:content_type]

test/storage/s3_test.rb

@@ -569,6 +569,12 @@ def counter
         assert_match %r{^http://s3\.amazonaws\.com/testing/avatars/original/5k\.png}, @dummy.avatar.url
       end
 
+      should "be rewinded after flush_writes" do
+        files = @dummy.avatar.queued_for_write.map{ |style, file| file.tap(&:read) }
+        @dummy.save
+        assert files.none?(&:eof?), "Expect all the files to be rewinded."
+      end
+
       context "and saved" do
         setup do
           object = stub