deny auth for blank password w/ ldap (previously just dumped)

thanks for the plugin. useful!

your version crashes and burns (500) if attempting to auth with a blank password against an ldap server. the dump points to one of the upstream modules not handling this case. i added a one-line fix that just refuses (401) to auth a blank password in ldap anonymous bind mode. i think this is an acceptable "feature"

also, i noticed you didn't have any tests for the ldap stuff. i added a test file with optional tests (direct and bridged both using anonymous bind) that only get executed if you set some environment variables first (for a working ldap host, basedn, and user:pass)

hope you find this useful
jay jay@purplewire.com