Convert NoMoreElementsException and EmptyQueueException to StateError.

lib/core/exceptions.dart

Index: lib/core/exceptions.dart
diff --git a/lib/core/exceptions.dart b/lib/core/exceptions.dart
index c09edb592ac01bf3956a48cd0b69342a28487e53..c1774ef1f139d4f821ba6bc882c0eeb9eacaff24 100644
--- a/lib/core/exceptions.dart
+++ b/lib/core/exceptions.dart
@@ -73,18 +73,6 @@ class NullPointerException implements Exception {
 }
 
 
-class NoMoreElementsException implements Exception {
-  const NoMoreElementsException();
-  String toString() => "NoMoreElementsException";
-}
-
-
-class EmptyQueueException implements Exception {
-  const EmptyQueueException();
-  String toString() => "EmptyQueueException";
-}
-
-
 class NotImplementedException implements Exception {
   const NotImplementedException([String message]) : this._message = message;
   String toString() => (this._message !== null