Added script to make list of headers

Added a new script with the purpose of getting all headers from a post's content and creating links for them in the left sidebar.
Some div classes have been modified, and a wrapper div has been added to posts because of this new script.
Some minor CSS changes have been made.

default.hbs

@@ -13,6 +13,9 @@
         <script src="{{asset "js/policy-popup.js"}}"></script>
         <script src="{{asset "js/arrow-fade.js"}}" async></script>
         <script src="{{asset "js/scroll-navbar-color.js"}}"></script>
+        {{#is "post"}}
+            <script src="{{asset "js/get-headers-list.js"}}"></script>
+        {{/is}}
 
         {{!--  TODO: REMOVE ON PRODUCTION! --}}
         <script type="text/javascript" src="http://livejs.com/live.js"></script>