Add headers task to Robo (#274)

Looks good, thank you @chrisdavenport 

If we ever have time (probably at the code sprint, added it to the todo-list), we should move the file existing check to the constructor.. We need that for every task 👍

RoboFile.php

@@ -523,4 +523,19 @@ class RoboFile extends \Robo\Tasks
 			->run()
 			->stopOnFail();
 	}
+
+	/**
+	 * Update copyright headers for this project. (Set the text up in the jorobo.ini)
+	 *
+	 * @return  void
+	 */
+	public function headers()
+	{
+		if (!file_exists('jorobo.ini'))
+		{
+			$this->_copy('jorobo.dist.ini', 'jorobo.ini');
+		}
+
+		(new \Joomla\Jorobo\Tasks\CopyrightHeader())->run();
+	}
 }