Upgrade highlight.js and enable new languages.

The bundle contains: CSS, Diff, HTML/XML, JSON, JavaScript,
Less, Plain text, Scala, SCSS, Shell Session, TypeScript.

Author: sjrd

_assets/css/bundle.css

@@ -2,3 +2,4 @@
 //= require highlight
 //= require font-awesome.min
 //= require style
+//= require highlight-custom

_assets/css/highlight-custom.css

@@ -0,0 +1,3 @@
+code.hljs {
+  background: none;
+}

_assets/css/highlight.css

@@ -1,7 +1,7 @@
 //= require clipboard.min
 //= require jquery.min
 //= require bootstrap.min
-//= require highlight.pack
+//= require highlight.min
 //= require lunr
 //= require highcharts
 //= require custom