Remove references to 'vendored plugins' except to note they used to exist but...

Remove references to 'vendored plugins' except to note they used to exist but are deprecated. 'gemified plugin' is the only supported option now.

guides/source/plugins.textile

@@ -25,16 +25,14 @@ endprologue.
 
 h3. Setup
 
-Before you continue, take a moment to decide if your new plugin will be potentially shared across different Rails applications.
+_"vendored plugins"_ were available in previous versions of Rails, but they are deprecated in
+Rails 3.2, and will not be available in the future. 
 
-* If your plugin is specific to your application, your new plugin will be a _vendored plugin_.
-* If you think your plugin may be used across applications, build it as a _gemified plugin_.
+Currently, Rails plugins are built as gems, _gemified plugins_. They can be shared accross 
+different rails applications using RubyGems and Bundler if desired. 
 
 h4. Generate a gemified plugin.
 
-Writing your Rails plugin as a gem, rather than as a vendored plugin,
- lets you share your plugin across different rails applications using
- RubyGems and Bundler.
 
 Rails 3.1 ships with a +rails plugin new+ command which creates a
  skeleton for developing any kind of Rails extension with the ability