Distinguish 'characters' from 'digits' in README
Distinguish 'characters' from 'digits' in README

The Yubikey token ID is 12 characters long, not 12 digits long. This 
can make it slightly confusing when first setting a key up, and in 
any case it's incorrect language.
Yubico/yubico-pam,madrat-/yubico-pam,eworm-de/yubico-pam,madrat-/yubico-pam,eworm-de/yubico-pam,Yubico/yubico-pam,madrat-/yubico-pam,Yubico/yubico-pam,eworm-de/yubico-pam