remove require-dev

Author: Yasuo Harada

composer.json

@@ -23,9 +23,6 @@
         "php": ">=5.3.0",
         "composer/installers": "*"
     },
-    "require-dev": {
-        "phpunit/phpunit": "3.7.*"
-    },
     "suggest": {
         "twbs/bootstrap": "Bootstrap framework"
     }