Add firewall access rules endpoint (#37)

* Add firewall access rules endpoint

* Configuration is an object

Maybe this needs to be defined in a seperate namespace (e.g. Cloudflare\API\Configuration) because it's no longer an array.

* Incorporate review

tests/Fixtures/Endpoints/deleteAccessRule.json

@@ -0,0 +1,12 @@
+{
+  "success": true,
+  "errors": [
+    {}
+  ],
+  "messages": [
+    {}
+  ],
+  "result": {
+    "id": "92f17202ed8bd63d69a66b86a49a8f6b"
+  }
+}