Add warning about not normalized quaternion

[Jiayuan-Gu]

https://github.com/haosulab/SAPIEN/blob/6bc3f4e2be910199b793f185aea5791d9f193e4c/src/utils/pose.hpp#L19 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.