Use groupattr value as is if no groupattr_regex defined. Closes #16
README update
ldapfull: Check for ldap group membership on login

Administrators can now supply a <group_dn> configuration directive. If
it is given, only users who are members of this group will be allowed to login

Signed-off-by: Tomasz Sterna <smoku@dcclabs.tv>
Grammear, spelling and other fixes for clarity.
Fixed out-conn-reuse s2s.xml option naming
Fix compilation errors introduced by -Werror
Fix typo in mm.c