We've changed some of the setting and some of the S3 tests got ignored.
This should make sure that the tests are really passing, after the
changes to IO Adapter.

This will prevent a pitfall as sometime the style's name can be a string.

Fixes #762

Fixes #846

Fixes #843

`aws-sdk` has been updated to support newer version of nokogiri, so we
should loosen our dependency.

* Force column reset in Rails >= 3.1
* Reuse another helper method

ContentTypeValidator now honors the `:allow_nil` and `:allow_blank` option.

This will ensure that the content type is a String.

Fixes #805

Make sure that we close opened files after we're done with them.

AttachmentAdapter now handles this for us.

Fix problem with incorrect content_type from `file` command

Fixed a typo in README.md.

Remove init.rb since plugins were deprecated and we don't support Rails 2.3 anymore

2.3 anymore