fixed delete_nodes for XDiGraph with multiedges=True
fixed delete_nodes for XDiGraph with multiedges=True

Fixes #28 again.

--HG--
extra : convert_revision : svn%3A3ed01bd8-26fb-0310-9e4c-ca1a4053419f/networkx/trunk%40180

SanketDG/networkx,dmoliveira/networkx,farhaanbukhsh/networkx,sharifulgeo/networkx,jakevdp/networkx,dmoliveira/networkx,chrisnatali/networkx,jfinkels/networkx,jtorrents/networkx,dmoliveira/networkx,beni55/networkx,dhimmel/networkx,OrkoHunter/networkx,jakevdp/networkx,kernc/networkx,ghdk/networkx,JamesClough/networkx,ionanrozenfeld/networkx,debsankha/networkx,nathania/networkx,ghdk/networkx,debsankha/networkx,tmilicic/networkx,Sixshaman/networkx,blublud/networkx,chrisnatali/networkx,sharifulgeo/networkx,yashu-seth/networkx,blublud/networkx,ghdk/networkx,kernc/networkx,cmtm/networkx,aureooms/networkx,kai5263499/networkx,jni/networkx,ionanrozenfeld/networkx,farhaanbukhsh/networkx,farhaanbukhsh/networkx,NvanAdrichem/networkx,jakevdp/networkx,goulu/networkx,sharifulgeo/networkx,bzero/networkx,jtorrents/networkx,aureooms/networkx,kai5263499/networkx,RMKD/networkx,nathania/networkx,jni/networkx,RMKD/networkx,harlowja/networkx,ionanrozenfeld/networkx,dhimmel/networkx,ltiao/networkx,michaelpacer/networkx,wasade/networkx,andnovar/networkx,blublud/networkx,kai5263499/networkx,chrisnatali/networkx,harlowja/networkx,jni/networkx,dhimmel/networkx,debsankha/networkx,nathania/networkx,aureooms/networkx,bzero/networkx,kernc/networkx,harlowja/networkx,jcurbelo/networkx,RMKD/networkx,bzero/networkx