In the last week, Andrew Shaw scored the decisive goal in a shootout victory against the hated Vancouver Canucks and the lone goal in a taut 1-0 victory against the Columbus Blue Jackets to keep the Blackhawks’ record season-opening point streak alive. That’s heady stuff for a 21-year-old checking-line center in his second NHL season, but Shaw is staying grounded. His veteran teammates make sure of it. ‘‘I can’t get ahead of myself,’’ Shaw said. ‘‘I’ve got to stay level-headed and make sure I’m grounded, and I compete and work hard. That’s my game. If you’re getting too cocky in …