Stablised exp link_function and quadrature variances
Stablised other quadrature (should speed things up also), added sampling ability to poisson
Merge branch 'params' of github.com:SheffieldML/GPy into params
Added a hack fix as suggested by max, zeroing any negative values (should really be numerically negative values on diagonal)
Merge branch 'params' of github.com:SheffieldML/GPy into params