Competition is heating up for Starbucks Corp. (Nasdaq: SBUX) as more independent and specialty coffee shops open around the country. But one analyst says the competition is too small and geographically concentrated to have much of an impact on the Seattle-based coffee giant. In fact, as artisan coffee becomes more popular, it may actually give Starbucks' new Reserve brand a boost, Morgan Stanley analyst John Glass wrote in a research note Wednesday. "The artisan segment of specialty coffee remains…