AFP/Getty Images Are markets getting dangerously bubblicious?If bull markets are born on pessimism, grow on skepticism, mature on optimism and die on euphoria, as famed investor John Templeton once said, then recent research from Bank of America Merrill Lynch offers cause for concern. Optimism reached its highest level on Wall Street since 2011 in June, according to strategists at B. of A., including equity and quantitative strategists Savita Subramanian and Dan Suzuki. The bank’s so-called sell-side indicator, which BAML says has been a reliable contrarian indicator, hit 56.4, rising 2.4 percentage points, and perhaps signaling that the bull market in U.S. stocks that is in its ninth year may be on its last legs via