Update Travis configuration

Author: Florian Eckerstorfer

.travis.yml

@@ -1,16 +1,28 @@
 language: php
 
-php:
-  - 5.3.3
-  - 5.3
-  - 5.4
-  - 5.5
-  - 5.6
-  - hhvm
+sudo: false
 
-before_script:
-  - composer --prefer-source install
-  - cp phpunit.xml.dist phpunit.xml
+matrix:
+  include:
+    - php: 5.3.3
+    - php: 5.3
+    - php: 5.4
+    - php: 5.5
+    - php: 5.6
+    - php: 5.6
+      env: COMPOSER_FLAGS='--prefer-lowest --prefer-stable'
+    - php: 7.0
+    - php: hhvm
+    - php: nightly
+  allow_failures:
+    - php: 7.0
+    - php: nightly
+  fast_finish: true
 
-script:
-  - phpunit
+before_install:
+  - travis_retry composer self-update && composer --version
+
+install:
+  - travis_retry composer update $COMPOSER_FLAGS --prefer-source -n
+
+script: vendor/bin/phpunit --verbose