Upgrade Travis configuration

.travis.yml

@@ -1,17 +1,19 @@
 language: php
 
 php:
-  - 5.3
-  - 5.4
-  - 5.5
   - 5.6
-  - hhvm
-
-matrix:
-    allow_failures:
-        - php: hhvm
+  - 7.0
+  - 7.1
+  - 7.2
+  - nightly
 
+matrix:
+  allow_failures:
+    - php: nightly
 
 before_script:
-  - wget http://getcomposer.org/composer.phar
-  - php composer.phar --dev install
+  - composer self-update
+  - composer update
+
+script:
+  - vendor/bin/phpunit

composer.json

@@ -42,6 +42,7 @@
     "name": "zetacomponents/base",
     "type": "library",
     "require-dev": {
+        "phpunit/phpunit": "~5.7",
         "zetacomponents/unit-test": "*"
     }
 }