title: How to detect if string contains only latin symbols using Ruby 1.9?
body: <p>I need to detect if some string contains symbols from a non latin alphabet. Numbers and special symbols like <code>-</code>, <code>_</code>, <code>+</code> are good. I need to know whether there is any non latin symbols. For example:</p>
  
  <pre><code>"123sdjjsf-4KSD".just_latin?
  </code></pre>
  
  <p>should return <code>true</code>.</p>
  
  <pre><code>"12333ыц4--sdf".just_latin?
  </code></pre>
  
  <p>should return <code>false</code>.</p>