Move RuboCop setup off Aliki branch

Author: capripot

.rubocop.yml

@@ -1,10 +1,6 @@
 #inherit_from:
 #  - .rubocop_todo.yml
 
-AllCops:
-  NewCops: disable
-  SuggestExtensions: false
-
 Metrics:
   Enabled: false
 Layout/LineLength:
@@ -44,9 +40,9 @@ Naming/VariableNumber:
   Enabled: false
 Naming/AccessorMethodName: # this creates breaking changes in the API
   Enabled: false
-Naming/PredicatePrefix: # this creates breaking changes in the API
+Naming/PredicateName: # this creates breaking changes in the API
   Enabled: false
-Lint/MissingSuper: # this doesn't exist in 1.8/1.9
+Style/MethodMissingSuper: # this doesn't exist in 1.8/1.9
   Enabled: false
 Style/MissingRespondToMissing: # this doesn't exist in 1.8/1.9
   Enabled: false

Gemfile

@@ -8,7 +8,6 @@ group :development do
   gem 'rake'
   gem 'rdoc', RUBY_VERSION < '2.7.0' ? '~> 6.0' : nil
   gem 'rspec'
-  gem 'rubocop', '~> 1.86' if RUBY_VERSION >= '2.7.0'
   gem 'simplecov' if RUBY_VERSION >= '2.7.0'
   gem 'webrick'
 end