title: Where can I find the version numbers of gems with the Ruby version it is compatible with?
body: <p>The question says it all. </p>
  
  <p>For example, I have a server with ruby 1.8.6 installed. And when I try <code>sudo gem install roo</code>, it gives an error <code>nokogiri requires Ruby version &gt;= 1.8.7</code>. So, I want to install an older version of <code>roo</code> which is compatible with <code>Ruby 1.8.6</code>. But I dont know where to search. I know of <code>RubyForge</code> but it also does not say about the compatible versions of Ruby.</p>