allow "pre" ending in matplotlib version string checking
allow "pre" ending in matplotlib version string checking

--HG--
extra : convert_revision : svn%3A3ed01bd8-26fb-0310-9e4c-ca1a4053419f/networkx/trunk%40778

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