Update rubocop requirement from 1.8.1 to 1.9.0 (#223)

* Update rubocop requirement from 1.8.1 to 1.9.0

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.8.1...v1.9.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

* Update .rubocop_todo.yml

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Santiago Traversa <santiago.traversa@gmail.com>

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2021-01-18 12:26:04 UTC using RuboCop version 1.8.1.
+# on 2021-01-29 12:53:33 UTC using RuboCop version 1.9.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new

Gemfile

@@ -5,7 +5,7 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'coveralls', require: false
-gem 'rubocop', '1.8.1', require: false
+gem 'rubocop', '1.9.0', require: false
 gem 'rubocop-performance', require: false
 gem 'rubocop-rake', require: false
 gem 'rubocop-rspec', require: false