title: Could not find railsties
body: <p>When I type</p>
  
  <pre><code>rails _4.2.0.rc2_ new hello_app
  </code></pre>
  
  <p>I get this error</p>
  
  <pre><code>/Library/Ruby/Site/2.0.0/rubygems/dependency.rb:315:in `to_specs': Could not find 'railties' (=  4.2.0.rc2) - did find: [railties-4.1.8] (Gem::LoadError)
  Checked in 'GEM_PATH=/Users/a11/.gem/ruby/2.0.0:/Library/Ruby/Gems/2.0.0:/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/gems/2.0.0', execute `gem env` for more information
  from /Library/Ruby/Site/2.0.0/rubygems/dependency.rb:324:in `to_spec'
  from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_gem.rb:64:in `gem'
  from /usr/bin/rails:22:in `&lt;main&gt;'
  </code></pre>
  
  <p>I tried installing railsties 4.2.0.rc2 using</p>
  
  <pre><code>gem install railties --pre
  </code></pre>