Fixes for Dart 2.10 (#42)

diff --git a/.travis.yml b/.travis.yml
index f0d3128..87be926 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,28 +1,24 @@
 language: dart
 
 dart:
- - preview/raw/2.10.0-0.2-dev
+ - dev
 
 jobs:
   include:
     - stage: analyze_and_format
       name: "Analyze"
-      dart: preview/raw/2.10.0-0.2-dev
       os: linux
       script: dartanalyzer --enable-experiment=non-nullable --fatal-warnings --fatal-infos .
     - stage: analyze_and_format
       name: "Format"
-      dart: preview/raw/2.10.0-0.2-dev
       os: linux
       script: dartfmt -n --set-exit-if-changed .
     - stage: test
       name: "Vm Tests"
-      dart: preview/raw/2.10.0-0.2-dev
       os: linux
       script: pub run --enable-experiment=non-nullable test -p vm
     - stage: test
       name: "Web Tests"
-      dart: preview/raw/2.10.0-0.2-dev
       os: linux
       script: pub run --enable-experiment=non-nullable test -p chrome
 
diff --git a/pubspec.yaml b/pubspec.yaml
index ea3cd61..abc21b5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -28,6 +28,10 @@
     git: git://github.com/dart-lang/charcode.git
   collection:
     git: git://github.com/dart-lang/collection.git
+  clock:
+    git: git://github.com/dart-lang/clock.git
+  fake_async:
+    git: git://github.com/dart-lang/fake_async.git
   js:
     git:
       url: git://github.com/dart-lang/sdk.git