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

pkg/dartdoc/test/markdown_test.dart

Index: pkg/dartdoc/test/markdown_test.dart
===================================================================
--- pkg/dartdoc/test/markdown_test.dart	(revision 14313)
+++ pkg/dartdoc/test/markdown_test.dart	(working copy)
@@ -3,13 +3,13 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// Unit tests for markdown.
-#library('markdown_tests');
+library markdown_tests;
 
 // TODO(rnystrom): Use "package:" URL (#4968).
-#import('../lib/markdown.dart');
+import '../lib/markdown.dart';
 
 // TODO(rnystrom): Better path to unittest.
-#import('../../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/