Merge pull request #823 from thomasNDS/patch-1

docs(navCtrl): miss quote in direction option example

ionic/components/nav/nav-controller.ts

@@ -220,7 +220,7 @@ export class NavController extends Ion {
    *      },{
    *       // here we can configure things like the animations direction or
    *       // or if the view should animate at all.
-   *       direction: back
+   *       direction: 'back'
    *      });
    *    }
    * }