[mod] github ribbon to about page

searx/templates/about.html

 {% extends 'base.html' %}
 {% block content %}
+{% include 'github_ribbon.html' %}
 <div class="row">
     <h1>About <a href="/">searx</a></h1>
 

searx/templates/github_ribbon.html

+<a href="https://github.com/asciimoo/searx" class="github">
+    <img style="position: absolute; top: 0; right: 0; border: 0;" src="/static/img/github_ribbon.png" alt="Fork me on GitHub"  class="github"/>
+</a>

searx/templates/index.html

 {% extends "base.html" %}
 {% block content %}
-<a href="https://github.com/asciimoo/searx" class="github">
-    <img style="position: absolute; top: 0; right: 0; border: 0;" src="/static/img/github_ribbon.png" alt="Fork me on GitHub"  class="github"/>
-</a>
+{% include 'github_ribbon.html' %}
 <div class="center">
     <h1 class="title">searx</h1>
     {% include 'search.html' %}