(mother and her child were homeless and petitioner took them into his home in January of 2007; they resided in spare room until October of 2007; mother was 21 and child was 2; no evidence that mother was full-time student for at least five months during year, so age requirement of I.R.C. Sec. 152 not satisfied and petitioner not entitled to claim mother as dependent; petitioner could claim mother's child as dependent).