Closes #678. Closes #450.

If a model has an existing attachment and styles, and later a new attachment is added (not just new styles), "rake paperclip:refresh:missing_styles" would crash with "TypeError: can't convert nil into Array".

#fingerprint now consistently returns nil before and after saving an attachment if the value can't be written to the db.

Add documentation for including `aws-sdk` in Gemfile

Add ':keep_old_files' option to `has_attached_file`

Set this option to `true` will make paperclip retain your file from the storage engine.

From https://github.com/pcreux/paperclip/commit/52374958ef83f1641cf008aead27c23b25fb842d

Conflicts:

	lib/paperclip/attachment.rb

This fixes #660

This is necessary so Gemnesium will be green.

Standardize strip with resy of application.  Without to_s, causes errors like "undefined method `strip' for image/bmp:MIME::Type".

In some case, we seriously don't want to prepend the timestamp with & if there wasn't a query string there. If the original URL doesn't have any query string, we should add the ?.

There was some problem with command line parsing with a special character.

The original commit came from @amazonwebservices and @trevorrowe in #579.
I had to revise the commit and make sure all the test cases are passing.
All credits still goes to those guys, thanks a lot!