Referendum page styling

[adborden]

Part of #18 to style the referendum page.

We want our jekyll site to look like the ODCA mocks and not necessarily the existing site. We should re-use the existing styles where possible but build towards the mocks if there is some divergence.

You can take a look at this branch for the disclosure-frontend converted LESS files in case it's helpful.

Help us shape our CSS architecture by documenting your work or suggesting better process and methods.