remove travis support (#143)

remove travis support
diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 37f57d2..4d33943 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -1,17 +1,17 @@
 name: Dart
 
 on:
-  push:
-    branches: [ $default-branch ]
   pull_request:
-    branches: [ $default-branch ]
+  push:
+    branches:
+      - master
 
 jobs:
   build:
     runs-on: ubuntu-latest
 
     container:
-      image:  google/dart:dev
+      image:  google/dart:beta
 
     steps:
       - uses: actions/checkout@v2
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 7777b6e..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,8 +0,0 @@
-language: dart
-dart: dev
-sudo: false
-script: ./tool/travis.sh
-
-branches:
-  only:
-    - master
diff --git a/pubspec.yaml b/pubspec.yaml
index 2ab40fb..46fa921 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -14,6 +14,5 @@
   path: ^1.4.0
 
 dev_dependencies:
-  grinder: ^0.8.0
   pedantic: ^1.9.0
   test: ^1.0.0
diff --git a/tool/grind.dart b/tool/grind.dart
deleted file mode 100644
index 3047616..0000000
--- a/tool/grind.dart
+++ /dev/null
@@ -1,35 +0,0 @@
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library usage.grind;
-
-import 'dart:io';
-
-import 'package:grinder/grinder.dart';
-
-final Directory _buildExampleDir = Directory('build/example');
-
-void main(List<String> args) => grind(args);
-
-@Task()
-void init() => _buildExampleDir.createSync(recursive: true);
-
-@Task()
-@Depends(init)
-void build() {
-  // Compile `test/web_test.dart` to the `build/test` dir; measure its size.
-  var srcFile = File('example/example.dart');
-  Dart2js.compile(srcFile,
-      outDir: _buildExampleDir,
-      minify: true,
-      extraArgs: ['--conditional-directives']);
-  var outFile = joinFile(_buildExampleDir, ['example.dart.js']);
-
-  log('${outFile.path} compiled to ${_printSize(outFile)}');
-}
-
-@Task()
-void clean() => delete(buildDir);
-
-String _printSize(File file) => '${(file.lengthSync() + 1023) ~/ 1024}k';