[FEATURE ember-routing-custom-link-view]

Allow usage of a custom view class from the `link-to` helper. This allows easier
customization of things like `classNameBindings`, `attributeBindings`, `active` state, etc
without having to reopen the core `Ember.LinkView` class.

Here is an example JSBin showing one potential use-case
(sending an action when active):

http://emberjs.jsbin.com/juzay/1/edit.