(petitioners, married couple, claimed first-time homebuyer tax credit on marital home purchased by husband on March 31, 2009; IRS denied credit because husband had owned home in prior three years; while wife did not own home in prior three years, husband could not claim qualification as long-term homeowner because purchase of marital home occurred before effective date of long-term homeowner provision in I.R.C. Sec. 36(c)(6) which applied only to purchases after November 6, 2009; thus, both spouses had to qualify as first-time homeowners under I.R.C. Sec. 36(c)(1) because statute includes parenthetical phrase "and if married, such individual's spouse" in the definition of the term "first-time homebuyer").