Fix gemspec

[joshuaspence]

Currently this gem fails to load because the aws-sdk is not declared as a dependency:

[!] There was an error while loading `hiera-eyaml-kms.gemspec`: cannot load such file -- aws-sdk
Does it try to require a relative path? That's been removed in Ruby 1.9. Bundler cannot continue.

 #  from /etc/puppet/vendor/bundle/ruby/2.3.0/bundler/gems/hiera-eyaml-kms-f223553dbd50/hiera-eyaml-kms.gemspec:4
 #  -------------------------------------------
 #  $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 >  require 'hiera/backend/eyaml/encryptors/kms'
 #
 #  -------------------------------------------

This diff fixes this issue and also bumps the AWS SDK to version 3.

[adenot]

Thanks for the PR.

I noticed it is rolling back the changes from PR #4 , was that on purpose or you made your changes based on an old revision?

[joshuaspence]

I didn't roll back the changes from #4, I just moved the profile option to the Aws::KMS::Client object. Otherwise I was getting the following error:

Error: Evaluation Error: Error while evaluating a Resource Statement, undefined method `access_key_id'

This error can be reproduced with the following code (running on an EC2 instance):

require 'aws-sdk-kms'

creds = Aws::SharedCredentials.new(profile_name: 'default')
kms = Aws::KMS::Client.new(region: 'ap-southeast-2', credentials: creds)
kms.decrypt({ciphertext_blob: ''})