Update rubocop

[yitsushi]

Reason: CVE-2017-8418 Low severity

[yitsushi]

One rspec test fails, but it fails on master too for me.

#251

  1) Moonshot::Stack#create under normal circumstances when template_s3_bucket is set should call put_object and create_stack with template_url parameter
     Failure/Error:
       s3_client.put_object(
         bucket: @config.template_s3_bucket,
         key: s3_object_key,
         body: template.body
       )

       #<InstanceDouble(Aws::S3::Client) (anonymous)> received :put_object with unexpected arguments
         expected: (hash_including(:bucket=>"rspec-bucket", :key=>"rspec-app-staging-1483228800-template.yml", :body=>"an instance of String"))
              got: ({:body=>"---\n- Resources: \n- Parameters:\n  - Parent1:\n    - Type: String\n    - Description: This...ent stack on create.\n", :bucket=>"rspec-bucket", :key=>"rspec-app-staging-1483225200-template.yml"})
       Diff:
       @@ -1,2 +1,5 @@
       -["hash_including(:bucket=>\"rspec-bucket\", :key=>\"rspec-app-staging-1483228800-template.yml\", :body=>\"an instance of String\")"]
       +[{:body=>
       +   "---\n- Resources: \n- Parameters:\n  - Parent1:\n    - Type: String\n    - Description: This is imported from the parent stack on create.\n",
       +  :bucket=>"rspec-bucket",
       +  :key=>"rspec-app-staging-1483225200-template.yml"}]

     # ./lib/moonshot/stack.rb:188:in `block in upload_template_to_s3'
     # ./lib/moonshot/stack.rb:187:in `upload_template_to_s3'
     # ./lib/moonshot/stack.rb:207:in `create_stack'
     # ./lib/moonshot/stack.rb:30:in `block in create'
     # ./lib/moonshot/stack.rb:25:in `create'
     # ./spec/moonshot/stack_spec.rb:124:in `block (5 levels) in <top (required)>'

[yitsushi]

PR checker fails on Ruby: 2.1:

$ gem update --system
Updating rubygems-update
Fetching: rubygems-update-3.0.3.gem (100%)
ERROR:  Error installing rubygems-update:
	There are no versions of rubygems-update (= 3.0.3) compatible with your Ruby & RubyGems
	rubygems-update requires Ruby version >= 2.3.0. The current ruby version is 2.1.0.
ERROR:  While executing gem ... (Errno::ENOENT)
    No such file or directory @ dir_chdir - /home/travis/.rvm/gems/ruby-2.1.10/gems/rubygems-update-2.7.8
The command "gem update --system" failed and exited with 1 during .

[marcingy]

@askreet Can we get your review on this please and a new release :)

[marcingy]

@askreet Reviews please ;)

[yitsushi]

Now travis is happy, but I would consider removing ruby 2.1 from the supported list instead.

https://www.ruby-lang.org/en/news/2017/04/01/support-of-ruby-2-1-has-ended/

There is no reason to keep 2.1 on this list. Such a good tool like Moonshot and would be a shame to drop off from projects because it can't follow ruby. If I start a new project with CLoudFormation, most likely I'll pick Moonshot because it's easy to use and so powerful. If Moonshot wants to stick with 2.1 (and any so old and not officially supported versions) just because we are afraid of cutting a version that will not working with older versions then I think Moonshot will start be a risk factor and will get a huge "consider the usage" on new projects which would be painful for everyone.