Cleanup exception handling

You're going to love this @joecohens and @jbrooksuk :)

app/Exceptions/Transformers/ModelNotFoundTransformer.php

@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * This file is part of Cachet.
+ *
+ * (c) Alt Three Services Limited
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace CachetHQ\Cachet\Exceptions\Transformers;
+
+use Exception;
+use GrahamCampbell\Exceptions\Transformers\TransformerInterface;
+use Illuminate\Database\Eloquent\ModelNotFoundException;
+use Symfony\Component\HttpKernel\Exception\HttpNotFoundException;
+
+/**
+ * This is the model not found transformer class.
+ *
+ * @author Graham Campbell <graham@alt-three.com>
+ */
+class ModelNotFoundTransformer implements TransformerInterface
+{
+    /**
+     * Transform the provided exception.
+     *
+     * @param \Exception $exception
+     *
+     * @return \Exception
+     */
+    public function transform(Exception $exception)
+    {
+        if ($exception instanceof ModelNotFoundException) {
+            $exception = new HttpNotFoundException('Resource not found');
+        }
+
+        return $exception;
+    }
+}