```ruby
dir 'core_gems'
download "bundler", "1.13.3"
download "msgpack", "1.0.2"
download "cool.io", "1.4.5"
download "http_parser.rb", "0.6.0"
download "yajl-ruby", "1.2.1"
download "sigdump", "0.2.4"
download "oj", "2.17.4"
download "tzinfo", "1.2.2"
download "tzinfo-data", "1.2016.8"
```

Use yajl-ruby 1.3.0 to support ruby 2.4
user
```ruby
dir 'core_gems'
download "bundler", "1.13.3"
download "msgpack", "1.0.2"
download "cool.io", "1.4.5"
download "http_parser.rb", "0.6.0"
download "yajl-ruby", "1.3.0"
download "sigdump", "0.2.4"
download "oj", "2.17.4"
download "tzinfo", "1.2.2"
download "tzinfo-data", "1.2016.8"
```
assistant