Lesley Mathis knows what her daughter said was wrong. But she never expected the 13-year-old girl would get arrested for it.The teenage girl made an offensive joke while chatting online with her classmates, triggering the school’s surveillance software.Before the morning was even over, the Tennessee eighth grader was under arrest. She was interrogated, strip-searched and spent the night in a jail cell, her mother says.Earlier in the day, her friends had teased the teen about her tanned complexio...