Fix PHPUnit testing on Travis (#89)

* update travis file

* Update phpunit

* Install phpunit on Travis

Author: Minishlink

.travis.yml

@@ -17,12 +17,12 @@ install:
   - npm install [email protected] -g
 
 before_script:
-  - composer install --prefer-source -n --no-dev
+  - composer install --prefer-source -n
   - "export DISPLAY=:99.0"
   - "sh -e /etc/init.d/xvfb start || echo \"Unable to start virtual display.\""
   - sleep 3 # give xvfb some time to start
 
 script:
   - web-push-testing-service start example -p 9012
-  - phpunit -c phpunit.travis.xml
+  - php ./vendor/phpunit/phpunit/phpunit -c phpunit.travis.xml
   - web-push-testing-service stop example

composer.json

@@ -22,7 +22,7 @@
     "guzzlehttp/guzzle": "^6.2"
   },
   "require-dev": {
-    "phpunit/phpunit": "4.8.*"
+    "phpunit/phpunit": "5.7.*"
   },
   "autoload": {
     "psr-4" : {