Switch to Rekognition API V2 and Fix Tests

Fixes #13 and #15

* Use Rekognition HTTPS endpoint by replacing RestClient with Faraday and Excon adapter
* Use file(1) to get image content type for `Faraday::UploadIO`
* Stub Faraday requests with VCR and update VCR configuration
* Remove unused VCR cassette requests
* When `Mustachio.face_data` receives a `Dragonfly::Job`, ensure a `temp_object` is set
* `Mustachio::Rekognition#face_detection` finds mouth not eyes
* `Mustachio.face_data` returns an `Array`
* Pend "#face_data_as_px" since big_mouth_x is not 5.0 within small_mouth_x * scale
* Pend specs which test commented code
* Ignore VIM swap files
* Add Travis CI