[README] added notes for using bwc.pl with MPI
[README] added notes for using bwc.pl with MPI

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs