composer: Add test script

For easier running of scripts. Now we can just execute `composer test`.

Author: jtojnar

.travis.yml

@@ -18,7 +18,7 @@ php:
 before_script:
   - composer install --dev
 
-script: vendor/bin/simple-phpunit --coverage-clover=coverage.clover
+script: composer test -- --coverage-clover=coverage.clover
 
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar

composer.json

@@ -33,5 +33,8 @@
         "branch-alias": {
             "dev-master": "1.0.x-dev"
         }
+    },
+    "scripts": {
+        "test": "vendor/bin/simple-phpunit"
     }
 }