Removing "?" and "=" from default output file name when fetching url

[raggaraluz]

This one fixes #458

[plexus]

The original issue (#458) is that when fetching a url like https://www.freesound.org/apiv2/sounds/2086/?format=json, it tries to save a file name ?format=json, which fails on Windows. This PR would change that to formatjson (I think?).

I haven't looked at this too deeply, but it looks like asset-path tries to find the last path segment (split on /). would it make more sense to drop any query params first, so that asset-path would save the above URL as 2086?

[plexus]

It looks like this has actually been fixed #487, so I'm going to close this. Feel free to reopen or open a new issue if this turns out to still be an issue. Thank you @raggaraluz for the patch!