Fix logo in header

Author: sbliven

_includes/header.html

@@ -1,6 +1,6 @@
 <!-- Header -->
 <header id="header"{% if page.layout == 'landing' %} class="alt"{% endif %}>
-  <h1><a href="{{ site.baseurl }}/index.html"><img src="images/logo/logo_100.png"/></a></h1>
+  <h1><a href="{{ site.baseurl }}/index.html"><img src="{{ site.baseurl }}/images/logo/logo_100.png"/></a></h1>
   <nav id="nav">
     <ul>
       <li class="special">