Basic UI design for admin page(s)

[zarino]

The admin UI is pretty minimal right now:

It's also spread quite thinly across three separate pages:

• an index page that handles login and listing of existing countries
• a new country page that lets you create a country from an EveryPolitician URL
• an existing country page that shows the country's name, github.io URL, and "force rebuild" button

I think the three pages could be combined into one. With some basic Bootstrap styling, to hold it together.

[zarino]

Pull request here: https://github.com/mysociety/political_tweets/pull/3