Adjust CustomBiomes to also include its config.xml file

CustomBiomes has a config.xml file that is associated with the mod
itself, not the biome data.

This change has config.xml installed with the mod, *not* its data. This
provides compatibility with newer CustomBiomes releases.
Merge pull request #174 from pjf/CustomBiomes

Adjust CustomBiomes to also include its config.xml file