Update composer.json

.travis/composer.json

 {
     "require": {
-        "phpunit/phpunit": "*",
         "ecomdev/mage-ci": "*"
     },
     "config": {
@@ -9,4 +8,4 @@
     "extra":{
         "magento-root-dir": "tests/magento"
     }
-}
+}
\ No newline at end of file