AndroidManifest: Request WRITE_EXTERNAL_STORAGE permission
The app crashes on Lollipop when trying to download files, but
it seems to work fine on Marshmallow. Officially, setDestinationUri()
is documented to require that permission but the other methods like
setDestinationInExternalFilesDir() are not - and since Marshmallow
they are intended to work without the permission, compare
See android@ed30deae5fe5b9de142b44933001c9b098c47712