Use Faraday as HTTP client (with Patron adapter).

This allows to:

- speed up requests by using licurl
- specify timeouts (handled by patron)
- use VCR to mock requests (HTTPParty not compatible with it)
Don't memoize faraday connection.

Because of a patron bug: https://github.com/toland/patron/issues/74
Merge pull request #8 from klacointe/faraday

Use Faraday as HTTP client (with Patron adapter).