Include data directory in gemspec files

This was missed by 7bc4cff, which resulted in version 0.16.0 of
`scss-lint` being broken.

Change-Id: I0cd42492b433ba0033889f722af2eaba7b7de0e4
Reviewed-on: https://gerrit.causes.com/32499
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Cut 0.16.1 release

Change-Id: Ib25821ef18861c4bfce88835b82f5bb6b4d3f7dc
Reviewed-on: https://gerrit.causes.com/32500
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>