Set Cache-Control header for Amazon S3 uploaded images to prevent

browsers from requesting images everytime.

--HG--
extra : convert_revision : svn%3Ab85faa78-f9eb-468e-a121-7cced6da292c%40477

scrapy/trunk/scrapy/contrib/pipeline/s3images.py

@@ -154,6 +154,7 @@ class S3ImagesPipeline(BaseImagesPipeline):
                 'X-Amz-Acl': 'public-read',
                 'X-Amz-Meta-Width': str(width),
                 'X-Amz-Meta-Height': str(height),
+                'Cache-Control': 'max-age=172800',
                 }
 
         buf.seek(0)