Update state.js

This feature was added to the codebase by pull request angular-ui#1809 but was never add in the documentation.

src/state.js

@@ -896,9 +896,11 @@ function $StateProvider(   $urlRouterProvider,   $urlMatcherFactory) {
      * - **`relative`** - {object=$state.$current}, When transitioning with relative path (e.g '^'), 
      *    defines which state to be relative from.
      * - **`notify`** - {boolean=true}, If `true` will broadcast $stateChangeStart and $stateChangeSuccess events.
-     * - **`reload`** (v0.2.5) - {boolean=false}, If `true` will force transition even if the state or params 
+     * - **`reload`** (v0.2.5) - {boolean=false|string=}, If `true` will force transition even if the state or params 
      *    have not changed, aka a reload of the same state. It differs from reloadOnSearch because you'd
      *    use this when you want to force a reload when *everything* is the same, including search params.
+     *    If string, string must be the name of the current state or one of its parent states, that way it is 
+     *    possible to target exactly which state's the resources need to be reloaded.
      *
      * @returns {promise} A promise representing the state of the new transition.
      *