Fix `scss-lint --version`

The `VERSION` constant wasn't being autoloaded, leading to embarassing
failures trying to run with the --version flag.

Change-Id: I75d66bc37752e9fcc0d98199fae90525b18fca7d
Reviewed-on: https://gerrit.causes.com/19905
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>