Update Survival Dataset to Pip

Hi,

Could please please update the survival dataset (and the corresponding function 'load_cox_gaussian_data()') to the latest pip version?

And also, I see there is a key called 'hr' in the gaussian_survival_data.h5 other than the three standard survival components 'x', 't', and 'e'. What does this "hr" stand for? 

Best,
Shi-ang