Replaced error log with exceptions

Author: thelfensdrfer

composer.json

@@ -6,7 +6,7 @@
 		"php": ">=7.2",
 		"ext-json": "*",
 		"voku/httpful": "0.4.*"
-	},
+    },
 	"require-dev": {
 		"phpunit/phpunit": "8.1.*"
 	},

src/InvalidRequestException.php

@@ -0,0 +1,6 @@
+<?php namespace VisualAppeal;
+
+class InvalidRequestException extends \Exception
+{
+    //
+}

src/InvalidResponseException.php

@@ -0,0 +1,6 @@
+<?php namespace VisualAppeal;
+
+class InvalidResponseException extends \Exception
+{
+    //
+}