Emit events for read receipts

lib/models/room.js

@@ -399,6 +399,10 @@ Room.prototype.addReceipt = function(event) {
             });
         });
     });
+
+    // send events after we've regenerated the cache, otherwise things that
+    // listened for the event would read from a stale cache
+    this.emit("Room.receipt", event, this);
 };
 
 function setEventMetadata(event, stateContext, toStartOfTimeline) {
@@ -527,3 +531,14 @@ module.exports = Room;
  *   var newName = room.name;
  * });
  */
+
+/**
+ * Fires whenever a receipt is received for a room
+ * @event module:client~MatrixClient#"Room.receipt"
+ * @param {event} event The receipt event
+ * @param {Room} room The room whose Room.name was updated.
+ * @example
+ * matrixClient.on("Room.receipt", function(event, room){
+ *   var receiptContent = event.getContent();
+ * });
+ */