fix bad canonical uri on pages (#354)

Fixes #98. We prepended too eagerly

Author: connor4312

_includes/head.html

@@ -13,6 +13,6 @@
     <link rel="stylesheet" href="{{ "/css/main.css" | prepend: site.baseurl }}">
     <link rel="shortcut icon" href="{{ "/img/favicon.png" | prepend: site.baseurl }}">
 
-    <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}">
+    <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.url }}">
     <link rel="alternate" type="application/rss+xml" title="{{ site.title }}" href="{{ "/feed.xml" | prepend: site.baseurl | prepend: site.url }}" />
 </head>