Merge pull request #10678 from prathamesh-sonpatki/typos

Fixed some typos

activerecord/CHANGELOG.md

-*   Also support extentions in PostgreSQL 9.1. This feature has been supported since 9.1.
+*   Also support extensions in PostgreSQL 9.1. This feature has been supported since 9.1.
 
     *kennyj*
 

railties/CHANGELOG.md

@@ -4,7 +4,7 @@
     *Arun Agrawal*
 
 *   Rails::Railtie no longer forces the Rails::Configurable module on everything
-    that subclassess it. Instead, the methods from Rails::Configurable have been
+    that subclasses it. Instead, the methods from Rails::Configurable have been
     moved to class methods in Railtie and the Railtie has been made abstract.
 
     *John Wang*

railties/lib/rails/tasks.rb

 $VERBOSE = nil
 
-# Load Rails rakefile extensions
+# Load Rails Rakefile extensions
 %w(
   annotations
   documentation