Add Rubocop extensions

Added the extensions:
* rubocop-performance
* rubocop-rake

Author: acant

.rubocop.yml

@@ -1,4 +1,7 @@
-require: rubocop-rspec
+require:
+  - rubocop-performance
+  - rubocop-rake
+  - rubocop-rspec
 
 AllCops:
   NewCops: enable

rspec-tabular.gemspec

@@ -36,6 +36,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'bundler-audit'
   spec.add_development_dependency 'license_finder'
   spec.add_development_dependency 'rubocop'
+  spec.add_development_dependency 'rubocop-performance'
+  spec.add_development_dependency 'rubocop-rake'
   spec.add_development_dependency 'rubocop-rspec'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'simplecov-lcov'