#14: whoops need to cast to array

- site:create timble --symlink textman only passes in 'all'
- putting back in place original type casting

src/Joomlatools/Console/Command/Extension/Install.php

@@ -53,7 +53,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
     {
         parent::execute($input, $output);
 
-        $extensions = $input->getArgument('extension');
+        $extensions = (array) $input->getArgument('extension');
 
         //https://regex101.com/r/fHlWZZ/1
         $re = '/[a-zA-Z0-9_.-].*\/[a-zA-Z0-9_.-]*:[?:(a-z-_#)?:(\>=\<=~^)(0-9).\*]*/';