send/recv are keyword inputs
runs_on requires v.value() not v.value()==1

In the case of a tie v.value can be .5.  This breaks the tie arbitrarily
add defaults for R, B, M in schedule
schedule passes kwargs to manydags for send, recv
print warning if status not optimal
set default makespan to 10000.0
add groupby
add orderings
add orderings to __init__.py