Add folder hierarchy and make code more behavioral

Author: yvoyer

CalculationHandler.php

@@ -13,8 +13,8 @@
         "phpunit/phpunit": "^5.2"
     },
     "autoload": {
-        "psr-0": {
-            "": ""
+        "psr-4": {
+            "Example\\": ["src", "tests"]
         }
     }
 }