Move RoomMember[] -> MemberEntry[] conversion somewhere sensible

This is required for automatically entering tab-complete mode because
onKeyDown is NOT called in that case, so we need to make sure to have a
membership list hanging around.

src/TabCompleteEntries.js

@@ -68,5 +68,34 @@ class MemberEntry extends Entry {
     }
 }
 
+MemberEntry.fromMemberList = function(members) {
+    return members.sort(function(a, b) {
+        var userA = a.user;
+        var userB = b.user;
+        if (userA && !userB) {
+            return -1; // a comes first
+        }
+        else if (!userA && userB) {
+            return 1; // b comes first
+        }
+        else if (!userA && !userB) {
+            return 0; // don't care
+        }
+        else { // both User objects exist
+            if (userA.lastActiveAgo < userB.lastActiveAgo) {
+                return -1; // a comes first
+            }
+            else if (userA.lastActiveAgo > userB.lastActiveAgo) {
+                return 1; // b comes first
+            }
+            else {
+                return 0; // same last active ago
+            }
+        }
+    }).map(function(m) {
+        return new MemberEntry(m);
+    });
+}
+
 module.exports.Entry = Entry;
 module.exports.MemberEntry = MemberEntry;