enable more es6 features for Espree
enable more es6 features for Espree

ldesplat/lab,AdriVanHoudt/lab,ldesplat/lab,ldesplat/lab,Marsup/lab,lloydbenson/lab,Marsup/lab,Marsup/lab,lloydbenson/lab,lloydbenson/lab,AdriVanHoudt/lab,AdriVanHoudt/lab