Network#create does not allow you to pass Excon overrides

[maschwenk]

It appears Network#create does not allow you to pass in Excon overrides like the other methods do. I think the fix would be separating the body from the opts
https://github.com/swipely/docker-api/blob/fc7ad57f77d59036dba9598ed52772778dc198c6/lib/docker/network.rb#L43-L48

Happy to open a PR to fix, just want to make sure I'm not misunderstanding