the name string is used multiple times in interpolation so storing it reduces object creation

this commit primarily uses frozen strings to reduce object creation during interpolation.
the :basename method now uses File.basename(file, ".*") rather than a Regexp. basename may be called multiple times.

by using the attachment name (symbol) and Class as keys we reduce the number of Strings created before hitting the cache

* Regression fix
* Add specs for intermediate_files var in Paperclip::Attachment

[fixes #1908]

Before the error message was sometimes millions of characters long.

> [paperclip] Content Type Spoof: Filename a.csv
> (application/octet-stream from Headers,
> [#<MIME::Type::Columnar:0x007f9f90f89fa8
> @container=#<MIME::Types:0x007f9f90b09d98 ... snip millions of
> characters of output here ...>], @content_type="text/csv",
> @raw_media_type="text", @raw_sub_type="csv", @simplified="text/csv",
> @i18n_key="text.csv", @media_type="text", @sub_type="csv",
> @extensions=["csv"]>] from Extension), content type discovered from
> file command: application/zip. See documentation to allow this
> combination.

Now becomes:

> [paperclip] Content Type Spoof: Filename a.csv
> (application/octet-stream from Headers,
> ["text/comma-separated-values", "text/csv"] from Extension), content
> type discovered from file command: application/zip. See documentation
> to allow this combination.

[fixes #2017]

Removes note for running paperclip in EOL'd version of Rails (2.3).

Removes `column_type` and `column_options` so that it works well in both
versions.

Backcported from master, to release a patch version with this bugfix.

[closes #1947]

[fixes #1977]

Removes `column_type` and `column_options` so that it works well in both
versions.

[closes #1947]

Turns out it didn't fix test failures like I thought. It only added
more!

This reverts commit b8221c6b.

Both v1 and v2 of the AWS Ruby SDK accept the string literal AES256, no need to differentiate. (thank you, @trevorrowe)

Further changes to Paperclip::Storage::S3 for choosing aws-sdk-v2 before aws-sdk-v1; use object.upload_file rather than object.put; implement v2 expiring_url method

According to the ImageMagick documentation the '@' flag is a special case that
can be used in conjunction with '>' to prevent IM from scaling an image up.
The '<' flag is ignored when using '@'.

http://www.imagemagick.org/Usage/resize/#pixel

This fixes the issue I reported in #1851

It should never be the case that `url` returns `nil`. If there is no url
that can be reasonable achieved, as is the case when the record the
attachment is attached to is unpersisted, then `url` should return the
default url.

[ci skip]

[ci skip]

For the full details of what is included in this release, check out NEWS.

[fixes #1875]

Thanks to MORI Shingo of DeNA Co., Ltd. for reporting this.

There is an issue where if an HTML file is uploaded with a .html
extension, but the content type is listed as being `image/jpeg`, this
will bypass a validation checking for images. But it will also pass the
spoof check, because a file named .html and containing actual HTML
passes the spoof check.

This change makes it so that we also check the supplied content type. So
even if the file contains HTML and ends with .html, it doesn't match the
content type of `image/jpeg` and so it fails.