feat(style): gapless border for blockquotes, fixes amsf/amsf-curtana#4

BREAKING CHANGE: Now paragraphs in a blockquote will get a single gapless border on the left side, you don't need special markup to achieve this now:

```markdown
> … these mean that in many fields the rule will be: Build it, and they will come.
>
> Paul Graham
```

_app/assets/themes/curtana/_less/app.less

@@ -436,6 +436,18 @@ body:hover .latest {
     > p {
       padding-left: .8em;
       border-left: 2px solid;
+      // TODO: Need better solution
+      // We will reset the common margin-bototm to get gapless borders for blockquotes
+      // This could help fix https://github.com/amsf/amsf-curtana/issues/4
+      padding-bottom: 1.6rem;
+      // Now reset default margin button from global define
+      margin-bottom: 0;
+
+      // Remove extra padding for the last element, re-apply margin
+      &:last-of-type {
+        padding-bottom: 0;
+        margin-bottom: 1.6rem;
+      }
 
       @media (max-width: @breakpoint-sm) {
         padding-left: calc(4vw - 2px);