fix: pandoc install under travis osx
fix: pandoc install under travis osx

SheffieldML/GPy,SheffieldML/GPy,dhhjx880713/GPy,mikecroucher/GPy,esiivola/GPYgradients,befelix/GPy,ysekky/GPy,SheffieldML/GPy,mikecroucher/GPy,ysekky/GPy,SheffieldML/GPy,esiivola/GPYgradients,ysekky/GPy,befelix/GPy,dhhjx880713/GPy,mikecroucher/GPy,ysekky/GPy,mikecroucher/GPy,dhhjx880713/GPy,esiivola/GPYgradients,befelix/GPy,dhhjx880713/GPy,befelix/GPy,esiivola/GPYgradients