add tests for conexp.util.graph
add tests for conexp.util.graph

fcatools/conexp-clj,exot/conexp-clj,exot/conexp-clj,exot/conexp-clj,exot/conexp-clj,fcatools/conexp-clj,fcatools/conexp-clj,exot/conexp-clj,fcatools/conexp-clj,fcatools/conexp-clj