Drop TravisCI for GitHub Actions

Update PHPUnit to v9
Update nix

.github/workflows/ci.yml

@@ -0,0 +1,37 @@
+name: ci
+
+on:
+  push:
+    branches:
+      - master
+      - github-actions
+      - ci
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  run:
+    runs-on: ${{ matrix.operating-system }}
+    strategy:
+      matrix:
+        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        php-versions: ["7.3", "7.4", "8.0"]
+    name: PHP ${{ matrix.php-versions }} Test on ${{ matrix.operating-system }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          extensions: bcmath
+          coverage: xdebug
+          tools: phpunit
+
+      - name: Install Composer dependencies
+        run: composer install --no-progress --prefer-dist --optimize-autoloader --no-dev
+
+      - name: PHP test
+        run: phpunit

README.md

@@ -1,6 +1,6 @@
 # dnsbl.php
 
-[![Build Status](https://travis-ci.org/jbboehr/dnsbl.php.png?branch=master)](https://travis-ci.org/jbboehr/dnsbl.php)
+[![GitHub Build Status](https://github.com/jbboehr/dnsbl.php/workflows/ci/badge.svg)](https://github.com/jbboehr/dnsbl.php/actions?query=workflow%3Aci)
 
 Simplified version of PEAR's Net_DNSBL with PEAR dependencies removed.
 

composer.json

@@ -22,6 +22,6 @@
   },
   "type" : "library",
   "require-dev": {
-    "phpunit/phpunit": "^7.4"
+    "phpunit/phpunit": "^9.4.2"
   }
 }