New plugin check_cpu; check_io_wait has been renamed to check_iowait

Signed-off-by: Davide Madrisan <davide.madrisan@gmail.com>
Update decumentation

Signed-off-by: Davide Madrisan <davide.madrisan@gmail.com>
Version 3

Signed-off-by: Davide Madrisan <davide.madrisan@gmail.com>