Modified lib/ldap_ou_to_group.rb

OU= pattern matching in parse_ou_from_dn(str) was case sensitive and is not compatible with some
LDAP servers. Added i flag makes the matching case insensitive.

On-the-fly user creation does not work with
authenticate_with_sync_ou_to_group. The issue was resolved by adding
return statement at the end of the function that relays the result
variable from authenticate_without_sync_ou_to_group.