Require Eigen-3.3.4.

Related to c++17 removed binder* functions.
Fixed in http://eigen.tuxfamily.org/bz/show_bug.cgi?id=1276
http://eigen.tuxfamily.org/index.php?title=ChangeLog#Eigen_3.2.10

Other binder* functions were removed only in the 3.3 branch.