fix a bug in the local driver

Author: zaherg

src/Backup/Classes/Drivers/LocalBackup.php

@@ -36,7 +36,7 @@ public function backup($databaseName)
 
  if ($this->options->compress) {
  $commands =[
- sprintf('cd $s', $this->options->path),
+ sprintf('cd %s', $this->options->path),
  sprintf('tar -zcf %1$s.sql.gz %1$s.sql', $databaseName),
  sprintf('rm -f %s.sql', $databaseName)
  ];