chore(docs): add code prettification

Closes #285

docs/app/js/code.js

@@ -0,0 +1,15 @@
+angular.module('code', [])
+
+.directive('code', function() {
+  return {
+    restrict: 'E',
+    terminal: true,
+    compile: function(element) {
+      var linenums = element.hasClass('linenum');// || element.parent()[0].nodeName === 'PRE';
+      var match = /lang-(\S+)/.exec(element[0].className);
+      var lang = match && match[1];
+      var html = element.html();
+      element.html(window.prettyPrintOne(html, lang, linenums));
+    }
+  };
+});