Enabled build matrix for GitHub Actions

.github/workflows/macos.yml

@@ -0,0 +1,13 @@
+name: macos
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Install dependencies
+      run: gem install minitest
+    - name: Run test
+      run: ruby -Ilib exe/rake

.github/workflows/ubuntu.yml

@@ -0,0 +1,20 @@
+name: ubuntu
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: [ '2.6.x', '2.5.x', '2.4.x', '2.3.x' ]
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up Ruby
+      uses: actions/setup-ruby@v1
+      with:
+        version: ${{ matrix.ruby }}
+    - name: Install dependencies
+      run: gem install minitest
+    - name: Run test
+      run: ruby -Ilib exe/rake

.github/workflows/windows.yml

@@ -0,0 +1,20 @@
+name: windows
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        ruby: [ '2.6.x', '2.5.x', '2.4.x' ]
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up Ruby
+      uses: actions/setup-ruby@v1
+      with:
+        version: ${{ matrix.ruby }}
+    - name: Install dependencies
+      run: gem install minitest
+    - name: Run test
+      run: ruby -Ilib exe/rake

.travis.yml

@@ -1,19 +1,12 @@
 language: ruby
 rvm:
-  - 2.0.0
-  - 2.1.10
-  - 2.2.10
-  - 2.3.8
-  - 2.4.5
-  - 2.5.3
-  - 2.6.1
   - ruby-head
   - jruby-9.2.4.0
   - jruby-head
 
 matrix:
   include:
-    - rvm: 2.5.3
+    - rvm: ruby-head
       env: COVERALLS=yes
 
 before_script: