Revert "Remove require for version file"

This reverts commit e94e9ced9db1e3d8a51063bf82da51ee71cdf499.
Revert "Back to string literal versioning"

This reverts commit deaf7d0cde1ebc081e56364bf777958b16ec94ba.
Rename VERSION file in gemspec to lib/gnip-rules/version.rb