Change the suggested password field from 32 to 40 chars

The SUGGESTED SCHEMA section suggests creating this password field
in the users table:

  password VARCHAR(32) NOT NULL

But the hashed password generated by Crypt::SaltedHash is 39 chars,
so if someone copies this table definition verbatim (like I did)
they will have a password field that is too short, resulting in a
truncated hash and no succesfull logins.
Merge pull request #18 from MagnusEnger/pod-password-length

Change the suggested password field from 32 to 40 chars