graph_utils seems to be out of date

[philtomson]

I wanted some way to visualize the graph and noticed graphs/graph_utils.jl which seems to have been the way graphs were visualized in the past. However, it seems to be out of date.

Had to add: using Printf in order for @sprintf to work.

Also notice that Chromosome is not defined anywhere:
ERROR: LoadError: UndefVarError: Chromosome not defined