Remember scroll position when navigating back, do not needlessly reload

entire timelines (only fetch since last known ID). Side effect: account
timelines no longer update in real-time

package.json

@@ -41,6 +41,7 @@
     "sinon": "^1.17.6"
   },
   "dependencies": {
-    "react-responsive": "^1.1.5"
+    "react-responsive": "^1.1.5",
+    "react-router-scroll": "^0.3.2"
   }
 }