Fixed a typo in README.rdoc

README.rdoc

@@ -31,7 +31,7 @@ User permissions are defined in an +Ability+ class. CanCan 1.5 includes a Rails
 
   rails g cancan:ability
 
-In Rails 2.3, just add a new class in `app/models/ability.rb` with the folowing contents:
+In Rails 2.3, just add a new class in `app/models/ability.rb` with the following contents:
 
   class Ability
     include CanCan::Ability