handle files links on /url renders
handle files links on /url renders

Not quite sure about this. It puts a soft requirement that notebooks must end with '.ipynb'.
Sage-Bionetworks/nbviewer,twosigma/beaker-sharing-server,Jay-Oh-eN/nbviewer,bollwyvl/nbviewer,twosigma/beaker-sharing-server,thomasyu888/nbviewer,franblas/beaker-sharing-server,iamjakob/nbviewer,roxyboy/nbviewer,imsparsh/nbviewer,franblas/beaker-sharing-server,Jay-Oh-eN/nbviewer,AlfiyaZi/nbviewer,thomasyu888/nbviewer,twosigma/beaker-sharing-server,iamjakob/nbviewer,twosigma/beaker-sharing-server,christophelec/nbviewer,imsparsh/nbviewer,bollwyvl/nbviewer,franblas/beaker-sharing-server,Sage-Bionetworks/nbviewer,christophelec/nbviewer,roxyboy/nbviewer,AlfiyaZi/nbviewer,franblas/beaker-sharing-server