Cache post data using sled

Each post fetch was taking 800ms TAT, so I'm using sled to fetch and
cache post data. This reduced TAT down to 2ms.

However, this could cause storage issues. I must design some sort of
resource manager to clean up cache.

templates/p.html

@@ -34,11 +34,8 @@
       <span><.= text .></span>
     <.}.>
   <.}.>
-
   <. if cur < p.text.len() {.>
     <.= p.text.slice(cur..) .>
   <.}.>
-
 <.}.>
 </p>
-<!-- markup.type_ = [ "CODE", "A", "EM", "STRONG" -->