The electric-vehicle company Tesla reported its best quarterly results ever Monday evening, but investors and analysts are greeting the news with measured optimism—a sign that Tesla is maturing as a company.Tesla reported $1.45 in adjusted per-share earnings for the second quarter, far higher than the roughly 95 cents analysts were looking for. Sales from regulatory credits—a source of revenue seen as less sustainable than sales of vehicles—-fell, but operating profits rose to record highs beca