A group of armed thugs slashed a 30-year-old tourist from Belgium in the face Saturday morning in an unprovoked attack at a Chelsea subway station, police said. The four or five assailants set upon the victim as she walked down the southbound staircase with a group of companions at 8:43 a.m. at the A/C/E station at West 23rd street and Eighth Avenue, police said. The attackers approached her and cut her face, leaving her with a wound that was treated at the scene, the NYPD said. The victim was seen talking to police after the attack with a bandage on...