Use GitHub actions for continuous integration (CI)

Bye bye Travis CI, you've served us well.

Author: SimonFrings

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  PHPUnit:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php:
+          - 5.6
+          - 5.3
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: xdebug
+      - run: composer install
+      - run: vendor/bin/phpunit --coverage-text
+
+  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

.travis.yml

@@ -1,4 +1,6 @@
-# clue/json-stream [![Build Status](https://travis-ci.org/clue/php-json-stream.svg?branch=master)](https://travis-ci.org/clue/php-json-stream)
+# clue/json-stream
+
+[![CI status](https://github.com/clue/php-json-stream/workflows/CI/badge.svg)](https://github.com/clue/php-json-stream/actions)
 
 A really simple and lightweight, incremental parser for [JSON streaming](https://en.wikipedia.org/wiki/JSON_Streaming)
 (concatenated JSON and [line delimited JSON](https://en.wikipedia.org/wiki/Line_Delimited_JSON)), in PHP.