Merge branch 'ruby-version-support' into 'master'

Enable .ruby-version support for development

See merge request gitlab-org/omnibus-gitlab!2488

.gitignore

@@ -6,7 +6,6 @@ pkg/*
 bin/*
 files/**/cache/
 vendor/cookbooks
-.ruby-version
 .ruby-gemset
 .rvmrc
 .rbenv-version

.gitlab-ci.yml

@@ -294,7 +294,7 @@ before_script:
 rubocop:
   stage: check
   <<: *dedicated-runner
-  image: ruby:2.3.3
+  image: ruby:2.3
   before_script:
     - bundle install -j $(nproc) --binstubs --path gems --without default test
   script:

.ruby-version

+ruby-2.3.7