title: Option[Map[String, String]] can get a value weirdly
body: <p>I found <code>Option[Map[String, String]]</code> works weirdly like this:</p>
  
  <pre><code> scala&gt; val fileInfo: Option[Map[String, String]] = Some(Map( "type" -&gt; "hoge" ))
   fileInfo: Option[Map[String,String]] = Some(Map(type -&gt; hoge))
  
   scala&gt; fileInfo.get("type")
   res1: String = hoge
  </code></pre>
  
  <p>I think the <code>Option</code> "get" method doesn't take any argument, so this is super weird for me. Why does it work? Is it an implicit conversion or a bug? I want to make sure how it works.</p>
  
  <p>My specifications are:</p>
  
  <ul>
  <li>Scala version 2.9.2 </li>
  <li>Java 1.6.0_43</li>
  </ul>