title: Can't create a database in Ruby on Rails
body: <p>I'm following some tutorials of association in rails database, the first step is to create the app with <code>rails new newProject -B</code>. Then i create the two models with <code>rails g scaffold Father name:string</code> and <code>rails g scaffold Child name:string sex:string father:references</code>.</p>
  
  <p>After that i try to create the database with the command <code>rake db:create</code>, but an error appears: </p>
  
  <blockquote>
    <p>Could not find nokogiri-1.6.7.1 in any of the sources Run <code>bundle
    install</code> to install missing gems.</p>
  </blockquote>
  
  <p>I run the command <code>bundle install</code> normally, but when i tried again, the same error appears.
  I tried to insert in the GemFile <code>gem 'nokogiri', '~&gt; 1.6', '&gt;= 1.6.7.1'</code> and the same error persists.</p>