New Highlight Container

Working on issue #147 while I waiting for #266 to get resolved.

Since this change is a major change from differing containers `<pre><code>...</code></pre>` to `<pre class="hljs">...</pre>`, I might as well make this pull request to show the changes. There are probably some documentation that needs to be updated after this so I won't merge in just yet.

But as of right now, everything seems to be working the same as master.