Updating to make data available on the page object

This update makes any data from any data files with the same name as the page filename available in the `page` object on the context:

`page1.json`:
```json
{
  "title": "Page 1"
}
```
`page1.hbs`:
```handlebars
---
heading: This is the first page
---
<h1>{{page1.title}} - {{page1.heading}}</h1>
```