Support rewriting direct twitter url -> full size url

If the user gives us the direct image url the twitter api is useless
since it doesn't have the status id. So just rewrite the url itself.

app/logical/downloads/rewrite_strategies/twitter.rb

@@ -3,19 +3,29 @@ module Downloads
     class Twitter < Base
       def rewrite(url, headers, data = {})
         if url =~ %r!^https?://(?:mobile\.)?twitter\.com!
-          url, headers = rewrite_image_url(url, headers)
+          url, headers = rewrite_status_page(url, headers)
+        elsif url =~ %r{^https?://pbs\.twimg\.com}
+          url, headers = rewrite_direct_image_url(url, headers)
         end
 
         return [url, headers, data]
       end
 
     protected
-      def rewrite_image_url(url, headers)
+      def rewrite_status_page(url, headers)
         source = ::Sources::Strategies::Twitter.new(url)
         source.get
         url = source.image_url
         return [url, headers]
       end
+
+      def rewrite_direct_image_url(url, headers)
+        if url =~ %r{^(https?://pbs\.twimg\.com/media/[^:]+)}
+          url = $1 + ":orig"
+        end
+
+        return [url, headers]
+      end
     end
   end
 end