Fix various rubocop/codeclimate issues

[tchia04]

This should fix the following issue at https://codeclimate.com/github/bundler/gemstash/builds/115

/usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:122:in `require': cannot load such file -- rubocop-performance (LoadError)
	from /usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:122:in `require'
	from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/config_loader_resolver.rb:15:in `block in resolve_requires'

[tchia04]

I don't know why the codeclimate is not working here. Maybe it's disabled?
It works fine in my fork at tchia04#2

[bronzdoc]

Hey @tchia04 We don't use codeclimate in this repo, so i don't really understand what is this fixing.

Seems like we do @olleolleolle? i have never seen that bot in any PR submited

[olleolleolle]

Thanks for this repair!

Could you make it a single commit?

[olleolleolle]

Tiny typo, should be "available"

[tchia04]

I am not sure how to squash all the commit into one. I counted the number of commits from HEAD and pass it to git rebase -i HEAD~X and it turns out to either pick up too many commits or too less commits. I believe there is an option to squash the commit on the merge button. Could you try that

[bronzdoc]

closed in favor of #241