Restructure pkg/unittest and pkg/webdriver to follow the pub conventions.

samples/markdown/test/markdown_test.dart

Index: samples/markdown/test/markdown_test.dart
===================================================================
--- samples/markdown/test/markdown_test.dart	(revision 14313)
+++ samples/markdown/test/markdown_test.dart	(working copy)
@@ -3,12 +3,12 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// Unit tests for markdown.
-#library('markdown_tests');
+library markdown_tests;
 
-#import('../lib.dart');
+import '../lib.dart';
 
 // TODO(rnystrom): Better path to unittest.
-#import('../../../pkg/unittest/unittest.dart');
+import '../../pkg/unittest/lib/unittest.dart';
 
 /// Most of these tests are based on observing how showdown behaves:
 /// http://softwaremaniacs.org/playground/showdown-highlight/