Redesign the post meta layout

- posted date
- updated date
- read time
- license statement of post bottom
- also refactor the `timeago.js`

_sass/layout/home.scss

@@ -74,10 +74,14 @@
     .post-meta {
       i {
         font-size: 0.73rem;
+
+        &:not(:first-child) {
+          margin-left: 1.2rem;
+        }
       }
 
-      span:not(:last-child) {
-        margin-right: 1.2rem;
+      em {
+        @extend %normal-font-style;
       }
     }