`>= 2.0.34` is the proper restriction. We weren't allowing `2.0.33`
before.

Paperclip 5 no longer supports aws-sdk v1. Having a lot of constraints
in one gem dependency caused issues when pushing the gem (ref:
https://github.com/rubygems/rubygems/issues/1564).

This commit simplifies the dependency restriction to `>= 2.0.33`.

Pairing with @kitop

File.exists? is deprecated and produces unecessary warning.

something in aruba 0.10.x is breaking the cucumber specs

something in aruba 0.10.x is breaking the cucumber specs

This reverts commit f6f5ea1b.

We upgraded the minimum required Ruby version to not include end-of-life
Rubies, but forgot to take into account that it's a backwards
incompatible change.

In this commit we rollback that change, allowing paperclip ~> 4.2.4 to
run on 1.9.2 again.

[fixes #1902]

A number of people were reporting that there were issues with the gem
dependency specifications changes we made recently. This will revert
them.

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

[fixes #1875]

Prioritize MimeMagic over the `file` binary for content type detection
when it finds a match. Fall back to `file` if MimeMagic can't match
anything.

`file` incorrectly detects Open Office XML files (e.g., xlsx, docx) as
zip since they're implemented as zipped archives of xml files. MimeMagic
detects them properly.

    bundle exec rake cucumber

to log

```
Capybara::RSpecMatchers::HaveText implements a legacy RSpec matcher
protocol. For the current protocol you should expose the failure messages
via the failure_message and failure_message_when_negated methods.
```

See
https://github.com/jnicklas/capybara/issues/1254
https://github.com/jnicklas/capybara/pull/1219

Remove RubyForge project name from gemspec

Updated gemspec to require aws-sdk gem ~> 1.6

Turns out that aws-sdk v2 isn't backwards compatible in the slightest,
so we should cap that at v1. And cucumber 1.3.17 was giving issues with
ruby 2.2.0. So let's update those.

Cocaine changes how it returns the supplied path in 0.5.5. While this
has no effect on the workings of Paperclip in a normal capacity, it does
break the tests. This change fixes that and updates the cocaine
dependency to 0.5.5.

This reverts commit ae3ec237.

This reverts commit 8d70c198.

```
 paperclip $ rspec spec/paperclip/integration_spec.rb --profile 1
Testing against version 4.1.7
.........................[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
.........

Finished in 15.19 seconds (files took 0.60155 seconds to load)
34 examples, 0 failures

Top 1 slowest examples (9.54 seconds, 62.8% of total time):
  Paperclip Many models at once does not exceed the open file limit
    9.54 seconds ./spec/paperclip/integration_spec.rb:18
```

to

```
 paperclip $ rspec spec/paperclip/integration_spec.rb --profile 1
Testing against version 4.1.7
.........................[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
.........

Finished in 10.95 seconds (files took 0.59585 seconds to load)
34 examples, 0 failures

Top 1 slowest examples (5.33 seconds, 48.7% of total time):
  Paperclip Many models at once does not exceed the open file limit
    5.33 seconds ./spec/paperclip/integration_spec.rb:18
```

at trim indent

This is a big one.

This change converts all of the existing tests from test/unit to RSpec.
It's been a long time coming, and was specifically prompted by the
inability of minitest to work with Appraisal across the various Rails
versions. Instead of ironing out that headache, converting to RSpec was
preferable (after initial probing).

Many assertions are still assertions and are housed in the Assertions
module, but they should be converted as they get touched. Similarly,
since we're touching all the tests/specs, we convert all the hashes from
1.8 syntax to 1.9 syntax.

pry-debugger doesn't compile on JRuby, and we're really only using that
locally.

Using the ActiveRecord validations is smart in order to lessen load on
the project to develop our own validators, but it's problematic in that
calling `valid?` on the record fires off all the other validations --
including those on fields which may not be set yet because of
mass-assignment. This commit will "pre-validate" the attachment's fields
so that it doesn't process an invalid attachment, but it does so by
running its validations manually on assignment.

This allows bundler to complete gem dependency resolution during
development. This is only relevant for paperclip developers. Please see:
https://github.com/thoughtbot/paperclip/issues/1256 and thanks to
@nkondratyev