It took a tweet to move Josh Harrellson’s feet. But the University of Kentucky center has gotten some major mileage from a single Twitter misstep. As No. 10 UK (4-1) prepares to host Boston University (4-3) tonight at Rupp Arena, Harrellson has emerged as a serviceable man in the middle for the Wildcats. And some of the strides he and backup Eloy Vargas have made on the court are the result of the steps they’ve taken during extra pre-practice conditioning.