docs(README): raise minimum angular version to 1.2 and add polyfill notice

Author: thgreasi

README.md

@@ -9,13 +9,14 @@ This directive allows you to sort an array with drag & drop.
 
 - JQuery
 - JQueryUI 1.9+
-- AngularJS
+- AngularJS 1.2+
 
 [Single minified cdn link](http://cdn.jsdelivr.net/g/jquery@1,[email protected]%28jquery.ui.core.min.js+jquery.ui.widget.min.js+jquery.ui.mouse.min.js+jquery.ui.sortable.min.js%29,[email protected],angular.ui-sortable) ~245kB and [example](http://codepen.io/thgreasi/pen/olDJi) with JQuery v1.x, required parts of JQueryUI v1.10, AngularJS v1.2 & latest angular-ui-sortable.
 
 **Notes:**
 > * JQuery must be included before AngularJS.  
 > * JQueryUI dependecies include [core](http://api.jqueryui.com/category/ui-core/), [widget](http://api.jqueryui.com/jQuery.widget/), [mouse](http://api.jqueryui.com/mouse/) & [sortable](http://api.jqueryui.com/sortable/). Creating a [custom build](http://jqueryui.com/download/#!version=1.10&components=1110000010000000000000000000000000) will [greatly reduce](https://github.com/angular-ui/ui-sortable/issues/154#issuecomment-40279430) the required file size. ([CDN](http://www.jsdelivr.com/) links for comparison: [full](http://cdn.jsdelivr.net/g/[email protected]) vs  [minimal](http://cdn.jsdelivr.net/g/[email protected]%28jquery.ui.core.min.js+jquery.ui.widget.min.js+jquery.ui.mouse.min.js+jquery.ui.sortable.min.js%29))
+> * User of AngularJS pre v1.2 can use the [$watchcollection polyfill](https://github.com/thgreasi/ng-watchcollection-polyfill).
 
 ## Usage