Simple helpers extension

Here's a quick hack to add a simple helpers system. Basically I'm looking for a way to add view "helpers" that are just shared functions available by default to all view templates.

This allows you to add `{helpers: {foo: function() { alert('heya!'); }}` to your Backbone.LayoutManager.configure block and have the function `foo` directly available in all view templates.

This could be far more advanced, but I figured the best way to get a conversation started about adding new features is with working code ;-)