Switch from travis to github actions

Author: W0rma

.github/workflows/ci.yaml

@@ -0,0 +1,37 @@
+name: ci
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  phpunit:
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version:
+          - "7.1"
+          - "7.2"
+          - "7.3"
+          - "7.4"
+          - "8.0"
+          - "8.1"
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: "Install PHP ${{ matrix.php-version }}"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          php-version: "${{ matrix.php-version }}"
+          coverage: "pcov"
+
+      - name: "Install dependencies with Composer"
+        uses: "ramsey/composer-install@v1"
+
+      - name: "Run PHPUnit"
+        run: "vendor/bin/simple-phpunit --coverage-text"

.travis.yml

@@ -1,8 +1,7 @@
 Negotiation
 ===========
 
-[![Build
-Status](https://travis-ci.org/willdurand/Negotiation.svg?branch=master)](http://travis-ci.org/willdurand/Negotiation)
+[![GitHub Actions](https://github.com/willdurand/Negotiation/workflows/CI/badge.svg)](https://github.com/willdurand/Negotiation/actions?query=workflow%3A%22CI%22+branch%3Amaster)
 [![Build
 status](https://ci.appveyor.com/api/projects/status/6tbe8j3gofdlfm4v?svg=true)](https://ci.appveyor.com/project/willdurand/negotiation)
 [![Total