Remove faraday dependency

Replaces faraday with Net::HTTP.

Given a URL like "http://www.nullrefer.com/?www.google.com", the latest version of faraday (0.9.0) attempts to use "www.google.com" as a query parameter with an empty value, which causes nullreferer.com to redirect to "www.google.com=". Net::HTTP does not, making unwind usable when other gems require a newer version of faraday, as well as removing a dependency.

VCR has also been updated, and uses webmock instead of the deprecated fakeweb.