Unconditionally re-encode locally-uploaded images to strip metadata

This strips metadata on file upload by re-encoding the files, at the cost
of possible slight image quality decrease and processing resources.

lib/paperclip/lazy_thumbnail.rb

@@ -20,7 +20,7 @@ def make
  private
 
  def needs_convert?
- needs_different_geometry? || needs_different_format?
+ needs_different_geometry? || needs_different_format? || needs_metadata_stripping?
  end
 
  def needs_different_geometry?
@@ -31,5 +31,9 @@ def needs_different_geometry?
  def needs_different_format?
  @format.present? && @current_format != @format
  end
+
+ def needs_metadata_stripping?
+ @attachment.instance.respond_to?(:local?) && @attachment.instance.local?
+ end
  end
 end