Add use of content's title as alternative title before default 'Document'

Looks at `Document`s content to match the first `# Title` and use it as an alternative page title.

Transforms this:
![screen shot 2014-03-28 at 5 39 04 pm](https://cloud.githubusercontent.com/assets/367429/2555019/5febb3e2-b6b9-11e3-8a5c-722542e250cc.png)

Into this:
![screen shot 2014-03-28 at 5 38 45 pm](https://cloud.githubusercontent.com/assets/367429/2555022/6ccd99cc-b6b9-11e3-9675-21d3683deadf.png)

And also page's html title although not seen on the screenshots.