Remote autosigner and check_sigul
    
    Robosignatory obsoleted autosigner and check_sigul was used to monitor
    the sigula availability during the autosigner development. Both scripts
    can be removed now. The possibly useful SubjectSMTPHandler() class was
    moved to block_retired.py which might use it.
    
    Signed-off-by: Till Maas <opensource@till.name>