add selflooped opt arg

Author: drbergman

src/metagraph.jl

@@ -249,6 +249,6 @@ function label_for(meta_graph::MetaGraph, code::Integer)
     return meta_graph.vertex_labels[code]
 end
 
-function transitiveclosure!(meta_graph::MetaGraph)
+function transitiveclosure!(meta_graph::MetaGraph, selflooped=false)
     throw(ArgumentError("transitiveclosure! not implemented for type MetaGraph"))
 end