minor #955 Update PHPUnit to its new major version (stof)

This PR was merged into the 2.0.x-dev branch.

Discussion
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Update PHPUnit to its new major version

4.0 and 4.1 would not be allowed by the ``~3.7`` constraint

Commits
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639f2132 Update PHPUnit to its enw major version

composer.json

@@ -44,7 +44,7 @@
         "doctrine/dbal": "~2.2",
         "swiftmailer/swiftmailer": "5.*",
         "monolog/monolog": "~1.4,>=1.4.1",
-        "phpunit/phpunit": "~3.7"
+        "phpunit/phpunit": "~4.0"
     },
     "suggest": {
         "symfony/browser-kit": ">=2.4,<2.6-dev",