[Docs] Force using current protocol scheme for resources and links

If the docs is accessed with https, change all links to be https as well.

docs/_pages/getting-started.md

@@ -134,4 +134,4 @@ For XLSX and ODS files, the number of rows per sheet is limited to *1,048,576*.
 
 ## Advanced usage
 
-You can do a lot more with {{ site.spout_html }}! Check out the [full documentation]({{ site.github.url }}/docs/) to learn about all the features.
+You can do a lot more with {{ site.spout_html }}! Check out the [full documentation]({{ site_url }}/docs/) to learn about all the features.

docs/_pages/guides.md

@@ -5,14 +5,14 @@ permalink: /guides/
 ---
 
 These guides focus on common and more advanced usages of {{ site.spout_html }}.<br>
-If you are just starting with {{ site.spout_html }}, check out the [Getting Started page]({{ site.github.url }}/getting-started/) and the [Documentation]({{ site.github.url }}/docs/) first.
+If you are just starting with {{ site.spout_html }}, check out the [Getting Started page]({{ site_url }}/getting-started/) and the [Documentation]({{ site_url }}/docs/) first.
 
 {% assign pages=site.pages | sort: 'path' %}
 <ul>
 {% for page in pages %}
   {% if page.title and page.category contains 'guide' %}
   <li>
-    <a class="page-link" href="{{ page.url | prepend: site.github.url }}">{{ page.title }}</a>
+    <a class="page-link" href="{{ page.url | prepend: site_url }}">{{ page.title }}</a>
   </li>
   {% endif %}
 {% endfor %}