fix: replacing np.power with np.square for efficiency
fix: replacing np.power with np.square for efficiency

befelix/GPy,ysekky/GPy,befelix/GPy,esiivola/GPYgradients,esiivola/GPYgradients,ysekky/GPy,SheffieldML/GPy,ysekky/GPy,befelix/GPy,ysekky/GPy,esiivola/GPYgradients,SheffieldML/GPy,esiivola/GPYgradients,SheffieldML/GPy,befelix/GPy,SheffieldML/GPy