Merge pull request #1 from petrkotek/phpunit6

Upgrade PHPUnit to 6.x & upgrade injector

Author: petrkotek

composer.json

@@ -25,7 +25,7 @@
     "require": {
         "php": ">=5.6",
         "bigcommerce/injector": "@stable",
-        "phpunit/phpunit": "^5.6"
+        "phpunit/phpunit": "^6.0"
     },
     "autoload": {
         "psr-4": {