tweaks to RuboCop config

.rubocop.yml

@@ -2,6 +2,7 @@ inherit_from: .rubocop_todo.yml
 
 AllCops:
   TargetRubyVersion: 2.3
+  DisplayStyleGuide: true
   Exclude:
     - 'test/scanners/**/*'
     - 'bench/example.ruby'

.rubocop_todo.yml

@@ -530,29 +530,6 @@ Naming/VariableNumber:
   Exclude:
     - 'test/unit/tokens.rb'
 
-# Offense count: 1
-Performance/Caller:
-  Exclude:
-    - 'lib/coderay/scanners/scanner.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Performance/Casecmp:
-  Exclude:
-    - 'rake_tasks/generator.rake'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Performance/StringReplacement:
-  Exclude:
-    - 'lib/coderay/encoders/html.rb'
-
-# Offense count: 3
-Performance/UnfreezeString:
-  Exclude:
-    - 'lib/coderay/encoders/encoder.rb'
-    - 'lib/coderay/encoders/html.rb'
-
 # Offense count: 1
 # Cop supports --auto-correct.
 # Configuration parameters: AutoCorrect.