move to php 5.5

Author: Emmanuel ROECKER

composer.json

@@ -16,12 +16,12 @@
         }
     ],
     "require": {
-        "php": ">=5.4",
+        "php": ">=5.5",
         "symfony/css-selector": "~2.3|~3.0"
     },
     "require-dev": {
-        "phpunit/phpunit": ">=4.8",
-        "satooshi/php-coveralls": ">=0.7"
+        "phpunit/phpunit": "~4.0",
+        "satooshi/php-coveralls": "~1.0"
     },
     "autoload": {
         "psr-4": {