Small tweaks to SDK constraint and travis (#11)

diff --git a/.travis.yml b/.travis.yml
index 468491a..963abdd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,20 +1,12 @@
 language: dart
 
-# By default, builds are run in containers.
-# https://docs.travis-ci.com/user/getting-started/#Selecting-infrastructure-(optional)
-# Set `sudo: true` to disable containers if you need to use sudo in your scripts.
-# sudo: true
-
 dart:
 - dev
-- stable
+- 2.0.0
 
-# See https://docs.travis-ci.com/user/languages/dart/ for details.
 dart_task:
   - test
 
-# Only run one instance of the formatter and the analyzer, rather than running
-# them against each Dart version.
 matrix:
   include:
   - dart: dev
diff --git a/pubspec.yaml b/pubspec.yaml
index 7156808..4abae3f 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,7 +5,7 @@
 homepage: https://github.com/dart-lang/clock
 
 environment:
-  sdk: '>=2.0.0-dev.36.0 <3.0.0'
+  sdk: '>=2.0.0 <3.0.0'
 
 dependencies:
   meta: '>=0.9.0 <2.0.0'