IMPORTANT: There is a bug in the current release of Fog (1.3.1) that will
return a broken expiring URL when the bucket name is valid for a subdomain.
This is fixed per https://github.com/fog/fog/pull/857 but not released
in the gem yet. I have added currently FAILING tests for these cases that
should pass when a new Fog is released.

This relates to #817

would cause the best_content_type to throw an error on trying nil.content_type.

This should fix an error when the user has turn on AWS logging while
and upload a file with non-English filename, as `aws-sdk` logger is not
encoding aware.

The problem was that the string returned from another logger methods
is in `US-ASCII`, while the string returned from Paperclip would be in
`UTF-8`. When the logger calls `#join` on those strings, Ruby would
raise an exception.

This solution is not the best, as it involves a monkey-patching, but
should make sure that the upload goes through without any hiccup. For
the long run, I'm going to send a patch to `aws-sdk` and also make
Paperclip require at least `aws-sdk > 1.4.1`

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

* 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.