This server only responds to posts. Try sending something like this:
curl -d '{"voting_system": "stv", "ballots": [{"count": 4, "ballot": ["orange"]}, {"count": 2, "ballot": ["pear", "orange"]}, {"count": 8, "ballot": ["chocolate", "strawberry"]}, {"count": 4, "ballot": ["chocolate", "sweets"]}, {"count": 1, "ballot": ["strawberry"]}, {"count": 1, "ballot": ["sweets"]}], "winners": 3}' http://vote.cognitivesandbox.com; echo;For further documentation, see the GitHub project page.