Changed the smbclient command used to fetch the free space available on the samba shares. Using du instead of ls, since it's much faster, specially with shares that have a lot of files.
Merge branch 'master' of https://github.com/rafaeldriutti/nagios-plugins

* 'master' of https://github.com/rafaeldriutti/nagios-plugins:
  Changed the smbclient command used to fetch the free space available on the samba shares. Using du instead of ls, since it's much faster, specially with shares that have a lot of files.

Closes #63.