Add shallow support to Link (#2012)

lib/link.js

@@ -26,7 +26,8 @@ export default class Link extends Component {
 
         return null
       }
-    ]).isRequired
+    ]).isRequired,
+    shallow: PropTypes.bool
   }
 
   componentWillReceiveProps (nextProps) {
@@ -40,6 +41,7 @@ export default class Link extends Component {
       return
     }
 
+    let { shallow } = this.props
     let { href, as } = this
 
     if (!isLocal(href)) {
@@ -64,7 +66,7 @@ export default class Link extends Component {
     const changeMethod = replace ? 'replace' : 'push'
 
     // straight up redirect
-    Router[changeMethod](href, as)
+    Router[changeMethod](href, as, { shallow })
       .then((success) => {
         if (!success) return
         if (scroll) window.scrollTo(0, 0)