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.

* Add failing test for case when no logger is specified
* add fix for failing test
* fix teardown of no logger test

In Rails, `ActionDispatch::Http::UploadedFile` has an accessor to access
a `Tempfile` object. However, `Rack::Test::UploadedFile` does not
provide that, but provinding the `#path` method instead. To be able to
support both, we have to check for existance for `#tempfile` method,
then fallback to `#path` method.

Fixes #807

It's not working correctly as expected, so let's revert this for now.

This reverts commit 51bb0f9f.