Refactory and new tests
Refactory and new tests

- Removing the self.api_server as it does not have anything with a
proxy and using the APIConsumer static class
- Add the following tests: test_enable_and_disable_proxy_with_toxic,
test_populate_creates_proxies_update_listen
- Call proxy.proxies() instead of proxy.proxies because we need to
ensure that we are fetching all the proxies

douglas/toxiproxy-python,douglas/toxiproxy-python