PROGRAM: modFreqs

DESCRIPTION: Change background frequencies of reversible tree model in such
a way that reversibility is maintained.

USAGE: modFreqs tree.mod <Afreq> <Cfreq> <Gfreq> <Tfreq> > new.mod
        OR
       modFreqs tree.mod <G+Cfreq> > new.mod

OPTIONS:
    --help, -h
        Print this help message.