Add integration tests for the gbfs.net client library

# Overview

The gbfs.net client library should have a suite of integration tests that run against a configurable GBFS feed.

# Implementation notes

See the integration tests for the [Syncromatics.Clients.Metro](https://github.com/syncromatics/Syncromatics.Clients.Metro/tree/master/tests/Syncromatics.Clients.Metro.Api.Tests) project for an example of such tests should be implemented.