fixed three tests by being _slightly_ less stringeent about poositive-definiteness
fixed three tests by being _slightly_ less stringeent about poositive-definiteness

dhhjx880713/GPy,esiivola/GPYgradients,gusmaogabriels/GPy,beckdaniel/GPy,mikecroucher/GPy,maaskola/GPy,avehtari/GPy,ysekky/GPy,ptonner/GPy,ptonner/GPy,avehtari/GPy,befelix/GPy,beckdaniel/GPy,befelix/GPy,beckdaniel/GPy,maaskola/GPy,jameshensman/GPy,avehtari/GPy,jameshensman/GPy,AlexGrig/GPy,jameshensman/GPy,AlexGrig/GPy,SheffieldML/GPy,beckdaniel/GPy,SheffieldML/GPy,maaskola/GPy,PredictiveScienceLab/GPy,dhhjx880713/GPy,strongh/GPy,SheffieldML/GPy,AlexGrig/GPy,gusmaogabriels/GPy,maaskola/GPy,TianpeiLuke/GPy,PredictiveScienceLab/GPy,befelix/GPy,Dapid/GPy,ptonner/GPy,TianpeiLuke/GPy,fivejjs/GPy,fivejjs/GPy,buntyke/GPy,PredictiveScienceLab/GPy,esiivola/GPYgradients,buntyke/GPy,buntyke/GPy,ptonner/GPy,jameshensman/GPy,strongh/GPy,Dapid/GPy,esiivola/GPYgradients,buntyke/GPy,mikecroucher/GPy,SheffieldML/GPy,Dapid/GPy,strongh/GPy,PredictiveScienceLab/GPy,Dapid/GPy,TianpeiLuke/GPy,mikecroucher/GPy,ysekky/GPy,mikecroucher/GPy,ysekky/GPy,esiivola/GPYgradients,ysekky/GPy,dhhjx880713/GPy,avehtari/GPy,AlexGrig/GPy,fivejjs/GPy,gusmaogabriels/GPy,dhhjx880713/GPy,befelix/GPy