Render descriptions and comments as Markdown

When displaying comments and descriptions for projects or stories,
render the content as Markdown before displaying it. This is a
simple way to support rich text descriptions and comments, and
there is no special editor as yet.

Any code in the supplied Markdown (indented by 4 spaces) will have
its syntax highlighted. The `highlightjs` module is used for syntax
highlighting and the `marked` module is used for parsing the
Markdown.

Also, stop eslint from raising an error when it thinks something is
undefined, and raise a warning instead. This is because the use of
`hljs` and `marked` was confusing the linter into thinking they
weren't defined.

Change-Id: I7896fd686a39e27f8068ee6db6747b2b5ab0ccfc

src/index.html

@@ -39,6 +39,8 @@
     <script src="moment/moment.js"></script>
     <script src="angular-moment/angular-moment.js"></script>
     <script src="angularjs-viewhead/angularjs-viewhead.js"></script>
+    <script src="marked/marked.min.js"></script>
+    <script src="highlightjs/highlight.pack.js"></script>
     <!-- endbuild -->
 
     <link rel="stylesheet" href="styles/main.css">