title: urllib.unquote_plus(s) does not convert plus symbol to space
body: <p>from the documents, the urllib.unquote_plus should replce plus signs by spaces.
  but when I tried the below code in IDLE for python 2.7, it did not.</p>
  
  <pre><code>&gt;&gt;s = 'http://stackoverflow.com/questions/?q1=xx%2Bxx%2Bxx'
  &gt;&gt;urllib.unquote_plus(s)
  &gt;&gt;'http://stackoverflow.com/questions/?q1=xx+xx+xx'
  </code></pre>
  
  <p>I also tried doing something like <code>urllib.unquote_plus(s).decode('utf-8').</code> 
  is there a proper to decode the url component?</p>