```ruby
dir 'core_gems'
download "bundler", "1.6.1"
download "json", "1.8.1"
download "msgpack", "0.5.8"
download "cool.io", "1.2.4"
download "http_parser.rb", "0.6.0"
download "yajl-ruby", "1.2.0"
```

Add rspec to avoid build failure
user
```ruby
dir 'core_gems'
download "bundler", "1.6.1"
download "json", "1.8.1"
download "msgpack", "0.5.8"
download "cool.io", "1.2.4"
download "http_parser.rb", "0.6.0"
download "yajl-ruby", "1.2.0"
download "rspec", "2.14.1"
```
assistant