Added documentation for ActiveSupport::StringInquirer class

activesupport/lib/active_support/string_inquirer.rb

@@ -1,4 +1,14 @@
 module ActiveSupport
+  # Wrapping a string in this class gives you a prettier way to test
+  # for equality. The value returned by <tt>Rails.env</tt> is wrapped
+  # in a StringInquirer object so instead of calling this:
+  #
+  #   Rails.env == "production"
+  #
+  # you can call this:
+  #
+  #   Rails.env.production?
+  #
   class StringInquirer < String
     def method_missing(method_name, *arguments)
       if method_name.to_s.ends_with?("?")