Use GitHub Actions for CI

.github/workflows/test.yml

@@ -0,0 +1,29 @@
+---
+name: Tests
+on: [ push, pull_request ]
+jobs:
+  test:
+    name: Test (Ruby ${{ matrix.ruby }}, Rails ${{ matrix.rails }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [ '2.0', '2.1', '2.2', '2.3', '2.4', '2.5', '2.6', 'jruby-9.1' ]
+        rails: [ '4.0.13', '4.1.16', '4.2.11.3', '5.0.7.2', '5.1.7', '5.2.0' ]
+        exclude:
+         - { ruby: '2.0', rails: '5.2.0' }
+         - { ruby: '2.0', rails: '5.1.7' }
+         - { ruby: '2.0', rails: '5.0.7.2' }
+         - { ruby: '2.1', rails: '5.2.0' }
+         - { ruby: '2.1', rails: '5.1.7' }
+         - { ruby: '2.1', rails: '5.0.7.2' }
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/ci.gemfile
+      RAILS_VERSION: ${{ matrix.rails }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - run: bundle exec rake

README.md

@@ -1,7 +1,7 @@
 Flip — flip your features
 ================
 
-[![Build Status](https://travis-ci.org/pda/flip.svg?branch=master)](https://travis-ci.org/pda/flip)
+[![Build Status](https://github.com/pda/flip/actions/workflows/test.yml/badge.svg?branch=master)](https://github.com/pda/flip/actions/workflows/test.yml)
 
 **Flip** provides a declarative, layered way of enabling and disabling application functionality at run-time.
 

gemfiles/rails5_0.gemfile → gemfiles/ci.gemfile

@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem "activesupport", "~>5.0.0"
+gem "activesupport", ENV.fetch('RAILS_VERSION')
 gem "i18n"
 
 gemspec path: "../"