Moved dependency to PHPUnit version to development dependencies

Requiring a specific version as runtime dependency makes conflicts with
other PHPUnit libraries (i.e. EcomDev_PHPUnit) very likely

Author: andreassimon

composer.json

@@ -10,6 +10,8 @@
         }
     ],
     "require": {
+    },
+    "require-dev": {
         "phpunit/phpunit": "4.2.*"
     },
     "bin": ["bin/phpunit-randomizer"],
@@ -21,4 +23,4 @@
             "dev-master": "1.0.x-dev"
         }
     }
-}
+}