Get rid of all the library tags.

lib/src/span_exception.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library source_span.span_exception;
-
 import 'span.dart';
 
 /// A class for exceptions that have source span information attached.
 class SourceSpanException implements Exception {
   /// A message describing the exception.
   final String message;
 
   /// The span associated with this exception.
   ///
   /// This may be `null` if the source location can't be determined.
@@ skipping 17 matching lines @@
 /// A [SourceSpanException] that's also a [FormatException].
 class SourceSpanFormatException extends SourceSpanException
     implements FormatException {
   final source;
 
   int get offset => span == null ? null : span.start.offset;
 
   SourceSpanFormatException(String message, SourceSpan span, [this.source])
       : super(message, span);
 }