Add link to pypi and a note about the update

download.html.in

@@ -36,6 +36,10 @@
 <p>You can also use pip:
 <code class="commands">sudo pip install --upgrade youtube_dl</code>
 </p>
+<p>
+This command will update youtube-dl if you have already installed it.
+See the <a href="https://pypi.python.org/pypi/youtube_dl">pypi page</a> for more information.
+</p>
 
 <p>To check the signature, type:
 <code class="commands">sudo wget @PROGRAM_URL@.sig -O youtube-dl.sig<br/>gpg --verify youtube-dl.sig /usr/local/bin/youtube-dl<br/>rm youtube-dl.sig</code>