[Rails] Improved the next steps to perform after installing compass so that it mentions registering the compass gem.

lib/compass/app_integration/rails/installer.rb

@@ -39,9 +39,20 @@ module Compass
             puts <<-NEXTSTEPS
 
 Congratulations! Your rails project has been configured to use Compass.
+Just one more thing left to do: Register the compass gem.
+
+In Rails 2.2 & 2.3, add the following to your evironment.rb:
+
+  config.gem "compass", :version => ">= #{Compass::VERSION}"
+
+In Rails 3, add the following to your Gemfile:
+
+  gem "compass", ">= #{Compass::VERSION}"
+
+Then, make sure you restart your server.
+
 Sass will automatically compile your stylesheets during the next
 page request and keep them up to date when they change.
-  Make sure you restart your server!
 NEXTSTEPS
           end
           if manifest.has_stylesheet?