added build, dist, egg dirs to .gitignore
added build, dist, egg dirs to .gitignore

depop/mongoengine-stripped,aszwemin/mongoengine,prijindal/mongoengine,Multiposting/mongoengine,Catstyle/mongoengine,newvem/mongoengine,alex/mongoengine,jimmyshen/mongoengine,ProgressivePlanning/mongoengine,ContextLogic/mongoengine,hmarr/mongoengine,reallistic/mongoengine,9nix00/mongoengine,muhammad-ammar/mongoengine,noirbizarre/mongoengine,elephanter/mongoengine,sourcelair/mongoengine,MakerReduxCorp/mongoengine,MakerReduxCorp/mongoengine,cogniteev/mongoengine,cogniteev/mongoengine,eli-b/mongoengine,ConsumerPhysics/mongoengine,Davidrjx/mongoengine,yarneo/mongoengine,conversocial/mongoengine,blaggacao/mongoengine,larsbutler/mongoengine,ContextLogic/mongoengine,WingGao/mongoengine,Davidrjx/mongoengine,starsirius/mongoengine,khallaghi/mongoengine,MongoEngine/mongoengine,MRigal/mongoengine,losintikfos/mongoengine,gmacon/mongoengine,touilleMan/mongoengine,nicolascine/mongoengine,nathanial/mongoengine,colinhowe/mongoengine,RussellLuo/mongoengine,gavincabbage/mongoengine,closeio/mongoengine,ms5/mongoengine,DavidBord/mongoengine,iandd0824/mongoengine,KarimAllah/mongoengine