README update (AWS SDK version)

Brings back warning on not supported SDK versions.

Related: https://github.com/thoughtbot/paperclip/commit/25be0b25d67923e28419c6146e8f8307741a974b#commitcomment-16831800

README.md

@@ -572,16 +572,13 @@ You may also choose to store your files using Amazon's S3 service. To do so, inc
 the `aws-sdk` gem in your Gemfile:
 
 ```ruby
-gem 'aws-sdk', '>= 2.0.0' # If using paperclip `master` (upcoming v5.0)
+gem 'aws-sdk', '>= 2.0.34'
 ```
 
 And then you can specify using S3 from `has_attached_file`.
 You can find more information about configuring and using S3 storage in
 [the `Paperclip::Storage::S3` documentation](http://www.rubydoc.info/gems/paperclip/Paperclip/Storage/S3).
 
-_**NOTE**: If upgrading aws-sdk from v1.x to v2.x, be sure to read the
-[UPGRADING guide](https://github.com/thoughtbot/paperclip/blob/master/UPGRADING)._
-
 Files on the local filesystem (and in the Rails app's public directory) will be
 available to the internet at large. If you require access control, it's
 possible to place your files in a different location. You will need to change

lib/paperclip/storage/s3.rb

@@ -121,6 +121,10 @@ module Paperclip
           e.message << " (You may need to install the aws-sdk gem)"
           raise e
         end
+        if Gem::Version.new(Aws::VERSION) >= Gem::Version.new(2) &&
+           Gem::Version.new(Aws::VERSION) <= Gem::Version.new("2.0.33")
+          raise LoadError, "paperclip does not support aws-sdk versions 2.0.0 - 2.0.33.  Please upgrade aws-sdk to a newer version."
+        end
 
         # Overriding log formatter to make sure it return a UTF-8 string
         if defined?(::Aws::Core::LogFormatter)