AT&T added new subscribers hand over fist in the second quarter, and free cash flow is rising.Shares of the telecommunications giant AT&T (T 4.92%) popped this morning after the company released second-quarter results showing strong subscriber growth and impressive free cash flow.AT&T's stock was up 4.9% as of 11:56 a.m. EDT.New subscribers and rising free cash flowAT&T's earnings and revenue were nothing to write home about this quarter. Sales fell slightly to $29.8 billion and were below analysts' consens ...