For most stocks, a 25% cut in an analyst's target price following an earnings release would send investors scrambling for the exit door. That wasn't the case with Bluebird Bio (BLUE -6.23%), however.The clinical-stage biotech saw a decent price rise after those two events in late March. What helped was that, despite the cut, said analyst believes the shares are on track to double in price and then some.The price target is cut. However...That prognosticator is Wells Fargo's Yanan Zhu, who now feels Bluebird ...