Made minor improvements to several platform operations; fixed minor bug

* Fixed incorrect number of arguments to a format() in Platform class
* Expanded linux.failed_logins input to also try sudo and /var/log/secure*
* Expanded linux.netstats input to also try sudo
* Expanded linux.users to try both /etc/shadow and /etc/passwd
* Added '-n' to sudo in cloudstream.cron_log.SSHProfile._input
Merge pull request #20 from jeandesmorts/correct_sudo_kludges

Made minor improvements to several platform operations; fixed minor bug