chore(docs): add blurb about ngAnimate

Closes #3887

Author: lgaudez

Diff for: README.md

@@ -27,6 +27,7 @@ Do you want to see directives in action? Visit http://angular-ui.github.io/boots
 # Installation
 
 Installation is easy as UI Bootstrap has minimal dependencies - only the AngularJS and Twitter Bootstrap's CSS are required.
+Note: Since version 0.13.0, UI Bootstrap depends on [ngAnimate](https://docs.angularjs.org/api/ngAnimate) for transitions and animations, such as the accordion, carousel, etc. Include `ngAnimate` in the module dependencies for your app in order to enable animation.
 
 #### Install with Bower
 ```sh