Add exclude path option to Raketask

[shortdudey123]

CircleCI installs gems to vendor/bundle instead of .bundle. This causes problems with checking yaml files if you check all yaml files by default.

YamlLint::RakeTask.new do |t|
  t.paths = %w(
    **/*.yml
    **/*.yaml
  )
  t.exclude_paths = %w(
    vendor/**/*.yml
  )
end