bundle install 报错：
There was a NoMethodError while loading logstash-input-rss.gemspec: undefined method metadata=' for #<Gem::Specification name=logstash
解决：
安装ruby新版：
http://blog.qianrushi.org/topic/59b600f21db485493d6cc384
bundle install 接着报错：
Could not find gem 'logstash-devutils' in any of the gem sources listed in your Gemfile.
解决：
安装 jruby
rvm install jruby
rvm use jruby-9.1.13.0 --default
gem install bundle
再次安装依赖包：
bundle install
成功
