Yelpapi

* Fix a few minor inconsistencies in the code.

* Revised to remove token/secret access and instead use API keys. Yelp will move to API keys only in March 2018. (courtesy tamos)
* An API key is now needed to instantiate a `YelpAPI` object. (courtesy tamos)
* Added support for 3 new endpoints:
* [Event Lookup API](https://www.yelp.com/developers/documentation/v3/event)
* [Event Search API](https://www.yelp.com/developers/documentation/v3/event_search)
* [Featured Event API](https://www.yelp.com/developers/documentation/v3/featured_event)
* `business_match_query` no longer assumes the country is the U.S. if the country code is missing.

* Implement new [Business Match API](https://www.yelp.com/developers/documentation/v3/business_match).
**NOTE**: This API is currently in beta. Yelp requires your app join the [Yelp Developer Beta Program](https://www.yelp.com/developers/v3/manage_app) to gain access to it.

* Remove reliance on `ez_setup.py`.
* Add `setup.cfg` to instruct the build process to build universal wheels.

* Implement the new Yelp Fusion API (aka Yelp v3 API). Note that yelpapi v1.4 is the last version to support the Yelp v2 API. [The Yelp v2 API is being deprecated, so all new developers should move to the new Fusion API ASAP.](https://engineeringblog.yelp.com/2017/02/recent-improvements-to-the-fusion-api.html)
* Use OAuth 2.0 for authentication.
* Implement new [Transaction Search API](https://www.yelp.com/developers/documentation/v3/transactions_search), [Reviews API](https://www.yelp.com/developers/documentation/v3/business_reviews), and [Autocomplete API](https://www.yelp.com/developers/documentation/v3/autocomplete).

* Use HTTPS for all API calls.
* Use new string formatter.
* Remove `YelpError` since the business API now returns a JSON error when given a bad business ID.