chore(test): migrate Dart tests to package:test

Instead of running with karma and the karma-dart shim, run dart
tests directly using the new package:test runner. This migrates
away from package:unittest.

Fixes a couple tests, mostly associated with depending on absolute
URLs or editing the test providers after an injector had already
been created.

Remove karma-dart and associated files. Change gupfiles to run tests
via `pub run test` instead.

modules/angular2/test/core/dom/dom_adapter_spec.ts

@@ -99,7 +99,7 @@ export function main() {
           DOM.removeChild(headEl, baseEl);
           DOM.resetBaseElement();
 
-          expect(baseHref).toEqual('/base');
+          expect(baseHref.endsWith('/base')).toBe(true);
         });
       });
     }

modules/angular2/test/core/dom/html5lib_adapter.server.spec.dart

@@ -1,7 +1,7 @@
 library angular2.dom.html5lib_adapter.test;
 
-import 'package:guinness/guinness.dart';
-import 'package:unittest/unittest.dart' hide expect;
+import 'package:guinness2/guinness2.dart';
+import 'package:test/test.dart' hide expect;
 import 'package:angular2/src/platform/server/html_adapter.dart';
 
 // A smoke-test of the adapter. It is primarily tested by the compiler.

modules/angular2/test/core/reflection/reflector_spec.ts

@@ -263,7 +263,7 @@ export function main() {
       describe("importUri", () => {
         it("should return the importUri for a type", () => {
           expect(reflector.importUri(TestObjWith00Args)
-                     .endsWith('base/dist/dart/angular2/test/core/reflection/reflector_spec.dart'))
+                     .endsWith('test/core/reflection/reflector_spec.dart'))
               .toBe(true);
         });
       });