Update core.py to improve speed greatly. This code is by Jason Grout   jason-sage@creativetrax.com Good work Jason!
Update core.py to improve speed greatly.
This code is by Jason Grout   jason-sage@creativetrax.com
Good work Jason!

--HG--
extra : convert_revision : svn%3A3ed01bd8-26fb-0310-9e4c-ca1a4053419f/networkx/trunk%401394

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