[Cookbook] Creating an Unbound Select

Adds a recipe for creating unbound selects that are useful for performance and integration with plugins.
Is this still an issue with [v. 1.8.0-beta.1](https://github.com/emberjs/ember.js/blob/v1.8.0-beta.1/CHANGELOG.md)? The addition of ember-metal (and eventually HTML Bars) handles the issue of script and metamorph tags everywhere and greatly improves performance. 

Just curious.