Merge pull request #24 from longnguyen2004/master

Fix wrong event type in `ConcurrentObservableSortedSet.Remove`

Swordfish.NET.CollectionsV3/ConcurrentObservableSortedSet.cs

@@ -83,7 +83,7 @@ public bool Remove(T value)
                   wasRemoved = newCollection != _internalCollection;
                   return newCollection;
               },
-              (index) => wasRemoved ? new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, value, index) : null
+              (index) => wasRemoved ? new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, value, index) : null
             );
             return wasRemoved;
         }