Even though Sentelligence Inc. in Noblesville has only five employees, the tiny tech firm offers an appealing benefits package rivaling that of a large corporation. The designer of diagnostic sensing devices for diesel engines has not discovered the Holy Grail of human resources. Rather, it’s using what’s known as a professional employer organization. Companies contract with PEOs to handle all the headaches of human resources, including payroll, payroll taxes, Worker’s Compensation claims, health plans, and other employee benefits, not to…