Clean up dead export tasks. Fixes #154.
Clean up dead export tasks. Fixes #154.

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