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

lib/unittest/core_matchers.dart

Index: lib/unittest/core_matchers.dart
===================================================================
--- lib/unittest/core_matchers.dart	(revision 10584)
+++ lib/unittest/core_matchers.dart	(working copy)
@@ -215,6 +215,11 @@
  * Type wrapper; e.g.:
  *
  *     expect(bar, new isInstanceOf<Foo>('Foo'));
+ *
+ * Note that this does not currently work in dart2js; it will 
+ * match any type, and isNot(new isInstanceof<T>()) will always
+ * fail. This is because dart2js currently ignores template type
+ * parameters.
  */
 class isInstanceOf<T> extends BaseMatcher {
   final String _name;