Update MacPorts jp2a links and instructions

Closes cslarsen/jp2a#11

source/jp2a/index.html

@@ -96,13 +96,10 @@ <h2>If you need to build jpeglib yourself</h2>
 
 <h2>macOS</h2>
 <div class="text">
-jp2a is part of <a href="https://www.macports.org">MacPorts</a>, so if you do a
-
+You can use <a href="https://ports.macports.org/port/jp2a">MacPorts</a>:
 <pre>
 sudo port install jp2a
 </pre>
-
-then everything should be installed.
 </div>
 
 <h2>FreeBSD</h2>
@@ -207,7 +204,7 @@ <h2>jp2a pages</h2>
 <li><a href="http://www.advogato.org/proj/jp2a/">jp2a on Advogato</a></li>
 <li><a href="http://www.linuxlinks.com/portal/cgi-bin/search.cgi?query=jp2a">jp2a on Linuxlinks</a></li>
 <li><a href="http://directory.fsf.org/jp2a.html">jp2a in the Free Software Foundation directory</a></li>
-<li><a href="http://jp2a.darwinports.com/">jp2a on DarwinPorts</a></li>
+<li><a href="https://ports.macports.org/port/jp2a">jp2a on MacPorts</a></li>
 <li><a href="http://linux.softpedia.com/get/Multimedia/Graphics/jp2a-14006.shtml">jp2a on Softpedia</a></li>
 <li><a href="http://aur.archlinux.org/packages.php?do_Details&amp;ID=5909">jp2a on AUR ArchLinux</a></li>
 <li><a href="http://www.opensoftware.pl/?q=node/219&amp;PHPSESSID=979e565f7ddf7a15fe355c1931434c47">jp2a on OpenSoftware</a> (in Polish)</li>