Test against phpunit-5.3

Author: malkusch

.travis.yml

@@ -9,6 +9,7 @@ cache:
 env:
   - PHPUNIT_VERSION=dev-master
   - PHPUNIT_VERSION=~5.3.0-dev
+  - PHPUNIT_VERSION=~5.3.0
   - PHPUNIT_VERSION=~5.2.0
   - PHPUNIT_VERSION=~5.1.0
   - PHPUNIT_VERSION=~5.0.0
@@ -40,6 +41,8 @@ matrix:
       php: 5.5
     - env: PHPUNIT_VERSION=~5.2.0
       php: 5.5
+    - env: PHPUNIT_VERSION=~5.3.0
+      php: 5.5
     - env: PHPUNIT_VERSION=~5.3.0-dev
       php: 5.5
     - env: PHPUNIT_VERSION=dev-master