If Taylor Swift can make her fans’ day by just repeatedly pushing the button for the 18th floor in an elevator and posting the video on Instagram, think of how this 6-year-old boy felt when the country-pop superstar paid him a personal visit in the hospital for a few hours. Jordan Nickerson, who has been battling leukemia, was treated yesterday to a personalized acoustic set and some quality time with Taylor at Boston Children’s Hospital. Taylor promised him, “I love singing songs for people, but I want to sing a song for you more than all the other people.”