Headers and footers in markup

This allows one to define the headers and footers in the markup. If there is a header/footer in the php configuration, the ones in the markup will override the ones in the config.

This closes #7.

To use:
```html
<script type="text/javascript">

	var h2pHeader = {
		height: "1cm",
		contents: '<div>{{pageNum}/{{totalPages}}</div>'
	}


	var h2pFooter = {
		height: "1cm",
		contents: '<div>{{pageNum}/{{totalPages}}</div>'
	}
</script>
```