default password hash should be "!"
fix docs on gid
add passwd line parser
add passwd and shadow line generators
add _group_for_user()
use bash as default shel
implement User.get_status()
document user groups
implement User.fix()
don't need password field from /etc/passwd
don't need line_shadow anymore
rewrite User.get_status() to return detailed info on item state
whitespace
avoid useless useradd
implement User.ask()