Add Eigen3 dependency for TravisCI
Add Eigen3 dependency for TravisCI

Milad-Rakhsha/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,dariomangoni/chrono,rserban/chrono,dariomangoni/chrono,rserban/chrono,Milad-Rakhsha/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,projectchrono/chrono,projectchrono/chrono,dariomangoni/chrono,dariomangoni/chrono,rserban/chrono,dariomangoni/chrono,rserban/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,rserban/chrono,rserban/chrono,rserban/chrono