Fixed bugs in add_edge! for multiedges
Fixed bugs in add_edge! for multiedges


git-svn-id: e2c0f9be234eb03bb44dac1dcb29a33d45fd6c14@9 6aa1fcdd-e81e-0410-86a3-8714df8c797d

bruce/graphy,bruce/graphy,chikamichi/plexus