Add to_enum unless block
Add Array#fetch
Merge pull request #1968 from suzukaze/add-to_enum-unless-block

Add to_enum unless block
Array#reverse_each should return Enumerator; ref #1968
Merge pull request #1969 from suzukaze/add-array.fetch

Add Array#fetch
Merge branch 'master' of github.com:mruby/mruby