修改博客标题图片地址，上次提交有误

Author: banyaner

_includes/header.html

@@ -2,7 +2,7 @@
 
   <div class="wrapper">
 
-    <a class="site-title" href="{{ site.baseurl }}/"><img src="https://github.com/banyaner/banyaner.github.io/blob/master/img/blog.png" alt="阿仲的博客"></a><!-- {{ site.title }} -->
+    <a class="site-title" href="{{ site.baseurl }}/"><img src="https://github.com/banyaner/banyaner.github.io/blob/master/img/blog.png?raw=true" alt="阿仲的博客"></a><!-- {{ site.title }} -->
 
     <nav class="site-nav">
       <a href="#" class="menu-icon">