Fixes #13: Increasing PHPUnit version and removing composer.lock

Author: fiunchinho

composer.json

@@ -12,7 +12,7 @@
     "require": {
     },
     "require-dev": {
-        "phpunit/phpunit": "4.2.*"
+        "phpunit/phpunit": "~4.2"
     },
     "bin": ["bin/phpunit-randomizer"],
     "autoload": {