Improve memory footprint of edge_dfs.
Improve memory footprint of edge_dfs.

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