Issue 51

Implements get_info described in #51 (closed).

Usage: curl -s --data '{"jsonrpc":"2.0", "method":"hive.get_info", "params":{}, "id":1}' http://127.0.0.1:8080

Expected result

{"jsonrpc": "2.0", "result": {"hivemind_version": "0.0.1", "hivemind_git_rev": "5c0b832", "database_schema_version": 18, "database_head_block": 4999997}, "id": 1}