Add link to old docs

[skip ci]

Author: c0bra

README.md

@@ -154,6 +154,8 @@ The full list of SauceLabs browsers can be seen by running `grunt saucebrowsers`
 
 As of the 3.0 release, 2.x is officially deprecated. There will be no further releases. If for some reason you need to find the 2.x source please see the [2.x branch](https://github.com/angular-ui/ui-grid/tree/2.x).
 
+The 2.x docs are here: [http://angular-ui.github.io/ui-grid/](http://angular-ui.github.io/ui-grid/).
+
 # Repository Rename
 
 With the 3.0 release, the repository has been renamed from "ng-grid" to "ui-grid".