Python 2.6 requires positioning by number of fragments in format.
Python 2.6 requires positioning by number of fragments in format.

This commit will restore Python 2.6 compatability.
sourcelair/mongoengine,ms5/mongoengine,gmacon/mongoengine,touilleMan/mongoengine,muhammad-ammar/mongoengine,gavincabbage/mongoengine,blaggacao/mongoengine,cogniteev/mongoengine,iandd0824/mongoengine,Davidrjx/mongoengine,yarneo/mongoengine,khallaghi/mongoengine,nicolascine/mongoengine,9nix00/mongoengine,prijindal/mongoengine,MongoEngine/mongoengine,MakerReduxCorp/mongoengine,DavidBord/mongoengine,elephanter/mongoengine,WingGao/mongoengine,ConsumerPhysics/mongoengine,larsbutler/mongoengine,nathanial/mongoengine,starsirius/mongoengine,RussellLuo/mongoengine,MRigal/mongoengine,losintikfos/mongoengine,cogniteev/mongoengine,Catstyle/mongoengine,MakerReduxCorp/mongoengine,eli-b/mongoengine,ProgressivePlanning/mongoengine,Davidrjx/mongoengine,reallistic/mongoengine,jimmyshen/mongoengine,noirbizarre/mongoengine