Fix attachment download

[edkedk99]

Hello,

It seems there is a small error in the following line, and I thought it was easier for the mantainer to just be informed rather than a pull request.

The send_file function in Flask changed its keyword parameter name: "attachment_filename" keyword argument, should be now "download_name" in the mentioned line

netviel/netviel/api.py

Line 124 in ad9eb0c

 attachment_filename=d["filename"]) 

And thank you for this app, it is very useful.

[David Straub]

Thanks, you're right, I would appreciate a pull request. It will also require setting a minimum flask version in setup.py.