Added tests for RMSE, NMAE and MAE.
Added tests for RMSE, NMAE and MAE.

Flowerowl/Crab,wnyc/crab,augustoppimenta/crab,hi2srihari/crab,echogreens/crab,wnyc/crab,rcarmo/crab,imouren/crab,Lawrence-Liu/crab,muricoca/crab,muricoca/crab