Load json data, allowing - to represent stdin.

def json_loads(data):
    """Load json data, allowing - to represent stdin."""
    if data is None:
        return ""

    if data == "-":
        return json.load(sys.stdin)
    elif os.path.exists(data):
        with open(data, 'r') as handle:
            return json.load(handle)
    else:
        return json.loads(data)