Issue #74

* Recipes mysql::ruby and postgresql:ruby, deprecated.
* Use database::mysql and database::postgresql for database cookbook
  library functionality.
Fix dependency on yanked modernizr gem

Version 6.4 of Gitlab depends on version 2.6.2 of the modernizr gem, which
is yanked. Therefore, the cookbook doesn't finish.

Changing the Gitlab and gitlab-shell versions fixes the issue.
Issue #76

* modernizr gem yanked
* bump version
Bump version to 6.9

* depsolv problem with modernizr
Rubocop