Yelpapi

* Raise [`HTTPError`](https://requests.readthedocs.io/en/latest/api/#requests.HTTPError) if one occurs (PR 25).

* Implemented new `close()` method to close the `requests.Session` object we use for performant API interactions. This can also be used as a context manager (this is the preferred way).
* Clarified [`README.md`](README.md) to make it clear that the user should always be sure to close the connection.

* Dropping EOL Python versions, adding newly-supported versions.
* Updating dependencies in [`requirements.txt`](requirements.txt).
* Updating project URL (moved from [gfairchild](https://github.com/gfairchild)'s personal namespace to [lanl](https://github.com/lanl)'s namespace).

* `match_type` parameter for the business match endpoint was deprecated on April 1, 2019 (see [Yelp's changelog](https://www.yelp.com/developers/v3/changelog)). (courtesy davebulaval)
* Added a check to ensure a required parameter, `address1`, is provided when using the business match endpoint. (courtesy davebulaval)
* Support for Python versions <3.4 is removed (i.e., this no longer works with Python 2.7). This is due to some dependencies that also have abandoned Python 2 support.

* Provided a means to set timeouts to API calls. (courtesy goodspark)
* Added unit tests, including Travis CI automation. (courtesy goodspark)

* Add better top-level documentation for `YelpAPI`.
* To avoid wasting API calls on obviously invalid requests, consistently check for parameters required for requests to succeed.