Add expresso script for npm test.
Add expresso script for npm test.

fxtentacle/tilemill,florianf/tileoven,Teino1978-Corp/Teino1978-Corp-tilemill,nyimbi/tilemill,fxtentacle/tilemill,MappingKat/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,Zhao-Qi/tilemill,fxtentacle/tilemill,Zhao-Qi/tilemill,tizzybec/tilemill,tilemill-project/tilemill,Zhao-Qi/tilemill,mbrukman/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,mbrukman/tilemill,nyimbi/tilemill,MappingKat/tilemill,mbrukman/tilemill,mbrukman/tilemill,tilemill-project/tilemill,isaacs/tilemill,fxtentacle/tilemill,paulovieira/tilemill-clima,MappingKat/tilemill,tizzybec/tilemill,paulovieira/tilemill-clima,Zhao-Qi/tilemill,isaacs/tilemill,fxtentacle/tilemill,tizzybec/tilemill,florianf/tileoven,MappingKat/tilemill,isaacs/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,tizzybec/tilemill,Zhao-Qi/tilemill,nyimbi/tilemill,mbrukman/tilemill,nyimbi/tilemill,paulovieira/tilemill-clima,florianf/tileoven,tilemill-project/tilemill,paulovieira/tilemill-clima,tizzybec/tilemill,nyimbi/tilemill,paulovieira/tilemill-clima