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

app/assets/javascripts/components/features/home_timeline/index.jsx

@@ -19,7 +19,7 @@ const HomeTimeline = React.createClass({
   render () {
     return (
       <Column icon='home' heading='Home'>
-        <StatusListContainer type='home' />
+        <StatusListContainer {...this.props} type='home' />
       </Column>
     );
   },

app/assets/javascripts/components/features/mentions_timeline/index.jsx

@@ -19,7 +19,7 @@ const MentionsTimeline = React.createClass({
   render () {
     return (
       <Column icon='at' heading='Mentions'>
-        <StatusListContainer type='mentions' />
+        <StatusListContainer {...this.props} type='mentions' />
       </Column>
     );
   },

app/assets/javascripts/components/features/ui/index.jsx

@@ -28,8 +28,8 @@ const UI = React.createClass({
         <MediaQuery minWidth={layoutBreakpoint}>
           <ColumnsArea>
             <Compose />
-            <HomeTimeline />
-            <MentionsTimeline />
+            <HomeTimeline trackScroll={false} />
+            <MentionsTimeline trackScroll={false} />
             {this.props.children}
           </ColumnsArea>
         </MediaQuery>