allow build_circuit to take router-hex-ids as well as Router instances
allow build_circuit to take router-hex-ids as well as Router instances

isislovecruft/txtorcon,david415/txtorcon,david415/txtorcon,isislovecruft/txtorcon,ghtdak/txtorcon,meejah/txtorcon,sammyshj/txtorcon,ghtdak/txtorcon,meejah/txtorcon,sammyshj/txtorcon