added target_param option to checkgrad(), removed unused function parameter
added target_param option to checkgrad(), removed unused function parameter

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