This year's trip to the Christmas tree lot was a little extra memorable for Jake Owen.  The country singer announced via Instagram on Friday, Dec. 4 that he is engaged to longtime girlfriend Erica Hartlein. He popped the question during the couple's Christmas tree outing and shared a number of photos from the special moment, including multiple glimpses at the ring.  "5 years ago we went and got our first Christmas Tree together....at this same spot," the 39-year-old "Barefoot Blue Jean Night" vocalist wrote. "This year, I asked her if she'd like to get Christmas Trees every year for the rest of our lives." The pics show that the couple's 19-month-old...