It is now a requirement for attachments to do one of three things:
  1. Have a content_type validation (e.g. "image/*")
  2. Have a filename validation (e.g. *.png, *.gif)
  3. Explicitly *not* have one of those validations

The intent is to make the default more secure, and you have to
explicitly reject the security of a validation in order to not have one.

This option was added to `has_attached_file` some time ago, see https://github.com/thoughtbot/paperclip/commit/65e8d4f6de50732d8e1b.

AbstractAdapter wasn't delegating `binmode` or `binmode?` to the
underlying @tempfile object. `binmode` is useful for cases where the
Adapter object gets handed on to another library expecting an `IO`
object holding image data. We ran into this with Prawn and people using
`prawnto` in conjunction with Paperclip. Prawn wants to ensure the `IO`
is in binmode for embedding the image data.

Use hexdigest to ensure that tempfile names will be a reasonable length.  Remove illegal filename characters check since it is no longer relevant when doing a hexdigest on the filename

When using S3 for storage, their data consistency model makes the
current behaviour of Attachment#reprocess! unreliable.

Apparently, Amazon can not guarantee that PUT's called after DELETE's
is actually executed in that order.

Hence, I propose preserving files, when doing a reprocces.

This ensures that multiline strings are properly matched in their
entirety.

Base64 encoded data-uris can contain newlines, make sure we handle
them correctly.

Content Type errors were incorrectly being set as an array on the base
attribute rather than being set individually as strings.

Copying attribute validation failures up to the root object breaks the
validate_attachment_presence_matcher when other paperclip validations
have failed.  This fixes this bug.

Also refactored to make the strategy hierarchy clearer

and memoize type_from_file_command