migrate from redcarpet to kramdown

This will stop github pages complaining on all page builds,
as github are deprecated all but kramdown for their markdown
engines.

Author: keithamus

_config.yml

@@ -5,14 +5,13 @@ description: |
 baseurl: "/chai-docs"
 
 safe: true
-markdown: redcarpet
-redcarpet:
-    extensions:
-      - no_intra_emphasis
-      - tables
-      - autolink
-      - strikethrough
-      - with_toc_data
+markdown: kramdown
+kramdown:
+  input: GFM
+  syntax_highlighter: rouge
+  syntax_highlighter_opts:
+    default_lang: js
+
 exclude:
   - node_modules
   - package.json

_sass/_main.scss

@@ -1743,3 +1743,11 @@ body.tests #mocha .test.fail h2:before {
   padding-right: 6px;
   color: #f00;
 }
+
+.highlight {
+  margin: 0;
+}
+
+.highlighter-rouge {
+  margin-bottom: 1.5em;
+}