Use GitHub actions for continuous integration (CI)

.gitattributes

@@ -1,6 +1,6 @@
 /.gitattributes export-ignore
+/.github/workflows/ export-ignore
 /.gitignore export-ignore
-/.travis.yml export-ignore
 /phpunit.xml.dist export-ignore
 /phpunit.xml.legacy export-ignore
 /tests export-ignore

.github/workflows/ci.yml

@@ -0,0 +1,43 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  PHPUnit:
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        php:
+          - 7.4
+          - 7.3
+          - 7.2
+          - 7.1
+          - 7.0
+          - 5.6
+          - 5.5
+          - 5.4
+          - 5.3
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+      - run: composer install
+      - run: vendor/bin/phpunit --coverage-text
+        if: ${{ matrix.php >= 7.3 }}
+      - run: vendor/bin/phpunit --coverage-text -c phpunit.xml.legacy
+        if: ${{ matrix.php < 7.3 }}
+
+  PHPUnit-hhvm:
+    name: PHPUnit (HHVM)
+    runs-on: ubuntu-18.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: azjezz/setup-hhvm@v1
+        with:
+          version: lts-3.30
+      - run: hhvm $(which composer) install
+      - run: hhvm vendor/bin/phpunit

README.md

@@ -1,4 +1,6 @@
-# graphp/algorithms [![Build Status](https://travis-ci.org/graphp/algorithms.svg?branch=master)](https://travis-ci.org/graphp/algorithms)
+# graphp/algorithms
+
+[![CI status](https://github.com/graphp/algorithms/workflows/CI/badge.svg)](https://github.com/graphp/algorithms/actions)
 
 Common mathematical graph algorithms implemented in PHP