Reports: Allow meta data about audits in response object

[ryelle]

Update the report result from each audit to be an object, instead of an array of arrays. This way, we can set some meta properties on each report, and avoid tying the HTML templates to the audits so tightly.

{
	name: 'Selectors',
	template: 'selectors',
	results: […],
}

This will now use the report.name in each section's <h2>. If template is set (it's optional), the corresponding file in templates/audits/ will be used to render this section. We can also re-use audit templates if the same layout will work for other audits, for example the display-none audit and selectors audit can both use the "selectors" template, since they both display a selector/file combo.

To test:

Run the audits. Replace test.css with your local test file(s).

CLI

npm run css-audit -- test.css --all --property-values=letter-spacing 

JSON

npm run css-audit -- test.css --all --property-values=letter-spacing --format=json

HTML

npm run css-audit -- test.css --all --property-values=letter-spacing --format=html --filename=test

[ryelle]

Now that #11's been merged, the templates changed - so I'll update this to fix the conflicts.