Remove Include from .rubocop.yml

`Gemfile` is already part of rubocop's default includes. If the
aim here was to overwrite the other includes (effectively excluding
them) then I think they should be explicitly excluded instead.

This commit also fixes offenses revealed by applying rubocop's more
exhaustive `Include` list

.rubocop.yml

@@ -1,6 +1,4 @@
 AllCops:
-  Include:
-    - 'Gemfile'
   Exclude:
     - 'Gemfile.devtools'
     - 'vendor/**/*'

Rakefile

@@ -16,23 +16,10 @@ namespace :metrics do
       --use rspec
       --zombie
     ]
-    arguments.concat(%W[--jobs 4]) if ENV.key?('CIRCLE_CI')
+    arguments.concat(%w[--jobs 4]) if ENV.key?('CIRCLE_CI')
 
     arguments.concat(%w[-- Mutant*])
 
-    success = Kernel.system(*arguments) or fail 'Mutant task is not successful'
-  end
-end
-
-desc 'Generate mutation operator listing'
-task :list do
-  require 'mutant'
-  # TODO: Add a nice public interface
-  registry = Mutant::Mutator::Registry.send(:registry)
-  registry.keys.select do |key|
-    key.is_a?(Symbol)
-  end.sort.each do |type|
-    mutator = registry.fetch(type)
-    puts '%-18s: %s' % [type, mutator.name.sub(/\AMutant::Mutator::Node::/, '')]
+    Kernel.system(*arguments) or fail 'Mutant task is not successful'
   end
 end

mutant.gemspec

@@ -10,9 +10,9 @@ Gem::Specification.new do |gem|
   gem.homepage    = 'https://github.com/mbj/mutant'
   gem.license     = 'MIT'
 
-  gem.require_paths    = %w[lib]
+  gem.require_paths = %w[lib]
 
-  mutant_integration_files   = `git ls-files -- lib/mutant/integration/*.rb`.split("\n")
+  mutant_integration_files = `git ls-files -- lib/mutant/integration/*.rb`.split("\n")
 
   gem.files            = `git ls-files`.split("\n") - mutant_integration_files
   gem.test_files       = `git ls-files -- spec/{unit,integration}`.split("\n")