A federal judge ruled yesterday to allow a massive class-action sexual discrimination lawsuit to move forward against Wal-Mart. 1.6 million current and former employees will be able to join the suit which is considered to be the largest civil rights case in the country’s history. The suit claims the country’s largest retailer systematically underpays female employees and offers women fewer opportunities for promotion. According to the lawsuit, 65 percent of the company’s hourly workers are women, but only 33 percent of its managers are.