Adds SearchService for assembling output for /search endpoint.

* SearchPage and ArticlePage models will take care of fetching pages and exposing
title and url fields.
Adds SearchPage and ArticlePage models responsible for scrapping MAS pages.

We need to perform 3 requests to find all the data we want:
* 1 request to search page to find article's page title and url;
* 1 request to article's url to find translation url;
* 1 request to translation url to get translated page title.

* Adds Faraday to fetch pages from remote service.
* Adds Nokogiri to parse pages to find relevant information.
* Adds VCR to mock requests in test mode.
Adds a very basic documentation.