Support Phpunit 7

Author: ssfinney

composer.json

@@ -22,7 +22,7 @@
     },
     "require-dev": {
         "mockery/mockery": "^0.9.1",
-        "phpunit/phpunit": "~4.0|~5.0",
+        "phpunit/phpunit": "~4.0|~5.0|~6.0|~7.0",
         "psy/psysh": "^0.5.1",
         "satooshi/php-coveralls": "^0.6.1|^1",
         "symfony/var-dumper": "~2.7|~3.0"