Add warning about not normalized quaternion

[Jiayuan-Gu]

SAPIEN/src/utils/pose.hpp

Line 19 in 6bc3f4e

Eigen::Matrix3f rotMat; // TODO(jigu): Maybe there exists an easier way to write it

We have not check whether quaternion is normalized when we create Pose. And to_transformation_matrix can in-place modify q. Thus, we are going to add some warning and perhaps automatically normalize for users.