user info returned by LDAPClient.Authenticate should be a map[string][]string

[ghost]

LDAPClient.Authenticate returns a map[string]string to describe user, however, items in ldap result attributes may contains more items, not just a string value.

In my case, I need all "memberOf" items of one user, but now I only got the first "memberOf" item.

So the user info returned by LDAPClient.Authenticate should be a map[string][]string to store all information.

I will commit some codes to fix it.