Remove optional dependency
Remove optional dependency

The tablib library shouldn't be installed by default because it's an optional dependency.

Dallinger/Dallinger,jcpeterson/Dallinger,Dallinger/Dallinger,jcpeterson/Dallinger,Dallinger/Dallinger,jcpeterson/Dallinger,Dallinger/Dallinger,jcpeterson/Dallinger,Dallinger/Dallinger,jcpeterson/Dallinger