After years of struggling, discount retailing giant Dollar Tree Inc DLTR could be crafting a genuine comeback story. What's more, it's not just empty words. Serious money is flowing into DLTR stock, both in the open market as well as in the options arena, implying that the rally still has legs.The most conspicuous clue that the turnaround may be genuine comes courtesy of Stewart Glendinning, Dollar Tree's chief financial officer. Recently, the executive bought 17,000 shares of DLTR stock at a per-share pric ...