Images in Subfolders

[benwr]

From @jay-pee in #7 , copying here as it's a slightly different issue

When putting images in subfolders an error occurs:

Traceback (most recent call last):
  File "c:\Users\Philip\Documents\GitHub\ankdown\ankdown\ankdown.py", line 389, in main
    cards_to_apkg(card_iterator, pkg_arg)
  File "c:\Users\Philip\Documents\GitHub\ankdown\ankdown\ankdown.py", line 343, in cards_to_apkg
    copyfile(abspath, newpath) # This is inefficient but definitely works on all platforms.
  File "C:\Python36\lib\shutil.py", line 121, in copyfile
    with open(dst, 'wb') as fdst:
FileNotFoundError: [Errno 2] No such file or directory: 'assets/images/philly-magic-garden.jpg'

Maybe we have to create the folder before putting the image there with copyfile(abspath, newpath).
Or change the newpath variable.