Fix last-spoke order

Turns out this timeline is the other way around, so loop through the other way

src/TabCompleteEntries.js

@@ -118,8 +118,7 @@ MemberEntry.fromMemberList = function(room, members) {
     // each member last spoke
     const lastSpoke = {};
     const timelineEvents = room.getLiveTimeline().getEvents();
-    for (var i = timelineEvents.length - 1; i >= 0; --i) {
+    for (const ev of room.getLiveTimeline().getEvents()) {
-        const ev = timelineEvents[i];
         lastSpoke[ev.getSender()] = ev.getTs();
     }
 

src/components/structures/RoomView.js

@@ -360,6 +360,10 @@ module.exports = React.createClass({
                 });
             }
         }
+
+        // update ther tab complete list as it depends on who most recently spoke,
+        // and that has probably just changed
+        this._updateTabCompleteList();
     },
 
     // called when state.room is first initialised (either at initial load,