Use URLs as node and edge list locations

[caufieldjh]

The current yaml format expects to be provided direct local paths to node and edge lists:
https://github.com/Knowledge-Graph-Hub/NEAT/blob/768cdf6d8bb9f069339e1c4d7519d0d73cfef15b/tests/resources/test.yaml#L8-L9
If it could be provided with URLs instead or additionally to local paths, remote runs of NEAT would be easier, since we assume it will have to retrieve node/edgelists from somewhere else anyway.

[justaddcoffee]

Discussion with Harry - at least two ways of doing this:

1. allow users to specify URLs in node_path and edge_path - this would require a regex or something to decide when something is a URL and when it's a file path
2. make a new pair of keys above graph called edge_url and node_url, use these to download the files and proceed as usual. These would have to live outside of the graph key, since the graph key/values are passed directory to Ensmallen

[justaddcoffee]

closed by #40

[justaddcoffee]

1. allow users to specify URLs in node_path and edge_path - this would require a regex or something to decide when something is a URL and when it's a file path

for the record, we ended up going with 1. above