make `res.sendfile()` more like `res.download()`. Closes #774
make `res.sendfile()` more like `res.download()`. Closes #774

1amageek/express,nodejs-camp/booklog-Zak,gnowoel/express,Lexine/express,supasate/express,danielrohers/express,v10258/express,gretac/express,za-creature/express,nathan818fr/express,simudream/express,nodejs-camp/booklog-tonebeta,codeforgeek/express,smcmurray/express,srichatala/express,grigorkh/express,yinhe007/express,hanweifish/express,sujianping/express,nodejs-camp/booklog-chle,nodejs-camp/booklog-leo,aifeld/express,dafabulousteach/express,nathan818fr/express,drzorm/express,adjohnson916/express,featurist/express,demohi/express,ZackBotkin/express,qq645381995/express,MoraLin/mora-test,dotnetCarpenter/express,buildsample/express,lmtdit/express,leiqiang75/express,andrejewski/express,vidyar/express,vnglst/express,jinghuizhai/express,caiocutrim/express,nodejs-camp/booklog-linkchen,weilixia/express,KodkodGates/express,awronka/express,tianhengzhou/express,countdracular/express,ahdinosaur/express,jenalgit/express,tyler-johnson/express,pshomov/express,xiaofuzi/express,buildsample/express,Talkyunyun/express,gdeividas/express,philxia/ex-tst-framework,caiocutrim/express,abdulhannanali/express,hacksparrow/express,BaggersIO/express,simudream/express,Ju2ender/express,bercanozcan/express,chuym/express,nodejs-camp/booklog-ben,vinodhalaharvi/express,philxia/ex-tst-framework,dotnetCarpenter/express,lmtdit/express,jenalgit/express,nodejs-camp/booklog-ansaga,pshomov/express,BaggersIO/express,blainsmith/express,Riokai/express,igarciaes/express,chrisinajar/express,kunalpict/express,WebStyle/express,dsupera13/express,dotnetCarpenter/express,PUSEN/express,heicx/express,Ju2ender/express,aifeld/express,evilboss/express,vnglst/express,nbeydoon/express,TestingCI/express,hdngr/express,demohi/express,nodejs-camp/booklog-ben,XueQian/express,TestingCI/express,stevemao/express,jinghuizhai/express,svnh/express,CrazySherman/express,friederbluemle/express,countdracular/express,sibura/express,ci-test2/express,nodejs-camp/booklog-homa,ci-test2/express,LestaD/express,Faiz7412/express,nodejs-camp/booklog-tonebeta-update,vnglst/express,flomotlik/express,andrejewski/express,rgrove/express,juandav/express,gnowoel/express,Faiz7412/express,sarvex/express,za-creature/express,hpcslag/express,nodejs-camp/booklog-chle,youprofit/express,auth0/express,nodejs-camp/booklog-Zak,tianhengzhou/express,Kevnz/express,mauricionr/express,benshiue/booklog-ben,xiaofuzi/express,evanlucas/express,isaacs/express,samuelcastro/express,lian774739140/express,svnh/express,WangCao/express,strongloop/express,PUSEN/express,dieuly/express,stewartml/express,corporateanon/express,tyler-johnson/express,Jonekee/express,maraoz/express,angelsanz/express,luxe-eng/valet-express.express,wtony/express,topaxi/express,sarvex/express,HXYNODE/express,devgeniem/express,dreamingblackcat/express,coreypnorris/express,methuz/express,mcanthony/express,Eric-Vandenberg/express,expressjs/express,gretac/express,qitianchan/express,pstrike/express,tjmehta/express,gnowoel/express,kawanet/express,evanlucas/express,luxe-eng/valet-express.express,udhayam/express,jymsy/express,r14r/fork_express_master,TestingCI/express,ericlu88/express,benshiue/booklog-ben,swstack/express,hdngr/express,svnh/express,coreypnorris/express,hanqingnan/express,XueQian/express,RickyDan/express,dafabulousteach/express,Jonekee/express,WangCao/express,jimmykuo/express,microlv/express,VegeChou/express,evilboss/express,XueQian/express,KodkodGates/express,nodejs-camp/booklog-jason,shanawarkhan/express,dafabulousteach/express,hacksparrow/express,lemelon/express,Eric-Vandenberg/express,vidyar/express,nodejs-camp/booklog-polo,kylezhang/express,mimaidms/express,heicx/express,micha149/express,HXYNODE/express,youprofit/express,btleffler/express,weilixia/express,kubrickology/express,LestaD/express,PeterWangPo/express,1amageek/express,kunalpict/express,grigorkh/express,andriyl/express,YR/express,corporateanon/express,RanadeepPolavarapu/express,elkingtonmcb/express,soyuka/express,hl198181/express,qitianchan/express,hanqingnan/express,listepo/express,JulyZhu/express,angelsanz/express,friederbluemle/express,samuelcastro/express,Ju2ender/express,rupanjanbaidya/express,Faiz7412/express,Matrixbirds/express,stevemao/express,maraoz/express,igarciaes/express,lemelon/express,awronka/express,1verson/express,michaeljunlove/express,CrazySherman/express,mikewesthad/express,mcanthony/express,wesleytodd/express,ZackBotkin/express,ralic/express,isaacs/express,Riokai/express,nodejs-camp/booklog-jollen,WebStyle/express,lian774739140/express,swarajgiri/express,soyuka/express,jenia0jenia/express,qitianchan/express,topaxi/express,r14r/fork_express_master,robomc/express,hpcslag/express,nbeydoon/express,gdeividas/express,nodejs-camp/booklog-ausir,junxiong/express,pathirana/express,KodkodGates/express,Ivanwangcy/express,r14r-work/fork_express_master,fuse-mars/express,evilboss/express,coreypnorris/express,blainsmith/express,stoskov/express,abhi3/express,blairzhang/express,Matrixbirds/express,nbeydoon/express,blakeembrey/express,nodejs-camp/booklog-ausir,nodejs-camp/booklog-to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