Added information about invoking migrations in non-default environmen…

…ts to NOTE box in the "Getting Started" guide

Reason: When the guide already mentions "default environment", I think it is more then appropriate to tell the whole story.

railties/guides/source/getting_started.textile

@@ -411,7 +411,7 @@ Rails will execute this migration command and tell you it created the Posts tabl
 ==  CreatePosts: migrated (0.0020s) ===========================================
 </shell>
 
-NOTE. Because you're working in the development environment by default, this command will apply to the database defined in the +development+ section of your +config/database.yml+ file.
+NOTE. Because you're working in the development environment by default, this command will apply to the database defined in the +development+ section of your +config/database.yml+ file. If you would like to execute migrations in other environment, for instance in production, you must explicitely pass it when invoking the command: <tt>rake db:migrate RAILS_ENV=production</tt>.
 
 h4. Adding a Link