use next_page_path and previous_page_path

Not only is this simpler, but it allows for changing of the default page paths.  For example if I want dashes in my page paths, I can set
`paginate_path: "/page-:num/"` in my _config.yml.

index.html

@@ -21,16 +21,12 @@ title: Home
 
 <div class="pagination">
   {% if paginator.next_page %}
-    <a class="pagination-item older" href="{{ site.baseurl }}page{{paginator.next_page}}">Older</a>
+    <a class="pagination-item older" href="{{paginator.next_page_path}}">Older</a>
   {% else %}
     <span class="pagination-item older">Older</span>
   {% endif %}
   {% if paginator.previous_page %}
-    {% if paginator.page == 2 %}
-      <a class="pagination-item newer" href="{{ site.baseurl }}">Newer</a>
-    {% else %}
-      <a class="pagination-item newer" href="{{ site.baseurl }}page{{paginator.previous_page}}">Newer</a>
-    {% endif %}
+    <a class="pagination-item newer" href="{{paginator.previous_page_path}}">Newer</a>
   {% else %}
     <span class="pagination-item newer">Newer</span>
   {% endif %}