Include path when both path and filename specified

[dstansby]

Currently if the filename and path are specified, path is ignored and the file is just downloaded to the current working directory. This should fix it. I've used pathlib because that's what I'm used to, not sure if it wants to be os.path.join instead.

[Cadair]

Can path be None here? (I think it can?)

[Cadair]

This has made me think a little more about the filename and path arguments here. I am fine with this change as it is, it still let's everything work and supports both arguments.

The only thing I wonder if it might be worth documenting is that this allows you to specify a full filepath to filename (joining with ./ does nothing if you specific an absolute path). What do you think about that? I know that filename != filepath and that using it like that is a little weird.

[dstansby]

The only precedence I can think of is urllib.request.urlretrieve, that only has a filename argument. https://docs.python.org/3.6/library/urllib.request.html#urllib.request.urlretrieve , but I think your suggestions works well too.

[dstansby]

The only precedence I can think of is urllib.request.urlretrieve, that only has a filename argument. https://docs.python.org/3.6/library/urllib.request.html#urllib.request.urlretrieve , but I think your suggestions works well too.

[Cadair]

Thanks @dstansby