Add rspec-rails
routes: stuffs should accept #destroy
Limit permitting parameters
edit_stuff_path has gone
Restore rendering _form for validation failures
Add stuffs controller spec (scaffold)
Stuff#file=: save uploaded file into files_dir

   p uploaded_file.original_filename #=> 'a.jpg'
   stuff.file = uploaded_file
   p stuff.filename #=> '20140524-161100-deadbeef.jpg'
   p File.exist?(stuff.filepath) #=> true
Add file_field