Abort Deployment when pre-deploy task fails. Addresses issue #29

docs/example-config/.mage/tasks/FailTask.php

@@ -0,0 +1,17 @@
+<?php
+namespace Task;
+
+use Mage\Task\AbstractTask;
+
+class FailTask extends AbstractTask
+{
+    public function getName()
+    {
+        return 'A Failing Task';
+    }
+
+    public function run()
+    {
+        return false;
+    }
+}