bumped minimum version of PHP to 5.5

.travis.yml

@@ -9,8 +9,6 @@ before_script:
 script: phpunit
 
 php:
-  - 5.3
-  - 5.4
   - 5.5
   - 5.6
   - hhvm

composer.json

@@ -16,7 +16,7 @@
         }
     ],
     "require": {
-        "php": ">=5.3.9",
+        "php": ">=5.5.9",
         "pimple/pimple": "~3.0",
         "symfony/event-dispatcher": "~2.6",
         "symfony/http-foundation": "~2.6",