Updated composer.json to use official PHPUnit package

Signed-off-by: Alex Bilbie <alex@alexbilbie.com>
diff --git a/composer.json b/composer.json
index dc098ac..7d60020 100644
--- a/composer.json
+++ b/composer.json
@@ -3,6 +3,6 @@
         "mikey179/vfsStream": "*"
     },
     "require-dev": {
-		"EHER/PHPUnit": "*"
+		"phpunit/phpunit": "*"
 	}
 }
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