Bugfixes and improvements

* Implemented the --image option
* Implemented the --write-state option to go with --check
* Fixed bug in Lockfile class

src/Configuration/SingleImageConfiguration.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace NoccyLabs\FreshDocker\Configuration;
+
+use Symfony\Component\Yaml\Yaml;
+
+class SingleImageConfiguration
+{
+
+    private $image;
+
+    public function __construct(string $image)
+    {
+        $this->image = $image;
+    }
+
+    public function getChecks(): array
+    {
+        return [ $this->image ];
+    }
+}