Update minimum versions required

Author: mnapoli

composer.json

@@ -17,9 +17,9 @@
     },
     "require": {
         "php": "^7.0",
-        "php-di/php-di": "^5.2",
-        "doctrine/cache": "^1.4",
-        "mindplay/composer-locator": "^2.1"
+        "php-di/php-di": "^5.4",
+        "doctrine/cache": "^1.6",
+        "mindplay/composer-locator": "^2.1.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.7"