Move a bunch of src/ files into subdirectories.

lib/src/runner/load_exception.dart

 // Copyright (c) 2015, 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 unittest.load_exception;
+library unittest.runner.load_exception;
 
 import 'dart:isolate';
 
 import 'package:path/path.dart' as p;
 
-import 'utils.dart';
+import '../utils.dart';
 
 class LoadException implements Exception {
   final String path;
 
   final innerError;
 
   LoadException(this.path, this.innerError);
 
   String toString() {
     var buffer = new StringBuffer('Failed to load "$path":');
@@ skipping 11 matching lines @@
           "Uncaught Error: Load Error: FileSystemException: ",
           "");
       innerString = innerString.split("Stack Trace:\n").first.trim();
     }
 
     buffer.write(innerString.contains("\n") ? "\n" : " ");
     buffer.write(innerString);
     return buffer.toString();
   }
 }