rubocop: Update deprecated class methods

.rubocop_todo.yml

@@ -6,13 +6,6 @@
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 5
-# Cop supports --auto-correct.
-Lint/DeprecatedClassMethods:
-  Exclude:
-    - '_plugins/contributors.rb'
-    - '_plugins/events.rb'
-
 # Offense count: 1
 Lint/LiteralAsCondition:
   Exclude:

_plugins/contributors.rb

@@ -105,7 +105,7 @@ module Jekyll
       end
 
       ## Create cache directory if it doesn't exist
-      if !File.exists?('_cache')
+      if !File.exist?('_cache')
         Dir.mkdir('_cache')
       end
 
@@ -117,7 +117,7 @@ module Jekyll
       # file has to be updated, they both get updated.
       corecontributors_cache = '_cache/corecontributors.marshall'
       sitecontributors_cache = '_cache/sitecontributors.marshall'
-      if File.exists?(corecontributors_cache) && File.exists?(sitecontributors_cache)
+      if File.exist?(corecontributors_cache) && File.exist?(sitecontributors_cache)
         corecontributors_cache_age = (Time.now - File.stat(corecontributors_cache).mtime).to_i
         sitecontributors_cache_age = (Time.now - File.stat(sitecontributors_cache).mtime).to_i
       else

_plugins/events.rb

@@ -66,7 +66,7 @@ module Jekyll
       end
 
       ## Create cache directory if it doesn't exist
-      if !File.exists?('_cache')
+      if !File.exist?('_cache')
         Dir.mkdir('_cache')
       end
 
@@ -78,7 +78,7 @@ module Jekyll
       events_file = '_events.yml'
 
       events_file_unix_time = File.stat(events_file).mtime.to_i
-      if File.exists?(conferences_cache)
+      if File.exist?(conferences_cache)
         conferences_cache_unix_time = File.stat(conferences_cache).mtime.to_i
       else
         conferences_cache_unix_time = 0