fixes fail backup and rotate with verifing default SSL certificate

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
apply pychecker and fixes invalid with that

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
increase version and update documents

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>