Tests are hard to debug

[Fishbowler]

There are a variety of nock'd domains.
When HTTP_PROXY is set to debug the real httpbin tests, it takes all nock traffic too, and requires a lot of configuration of NO_PROXY (or just some faith in the tests that don't complete) that things are working.

Move all nock'd domains to a single host for easier configuration in a development environment.

[paulmelnikow]

Sounds good to me!

It seems like we should also remove mock_request which is deprecated, and replace everything with nock. Does that make sense?

[paulmelnikow]

Also! If we switch over to using promises and promise-based tests, we should be able to make our test setup should easier to reason about. Instead of .toss()-ing the tests we can make a .run() method that returns a promise and in most of our tests, invoke that.

[Fishbowler]

Started work on this.

[paulmelnikow]

I'm convinced adding this run() method is really important. It'll make our tests much better and it'll make it way nicer to use the library downstream. Let's tackle that after we clear the PR backlog.

[paulmelnikow]

run() added in #183 and most of the tests rewritten in #186 in a way that's way friendlier. mock-request is no longer being used.

Probably what's left is to rewrite the httpbin tests using local endpoints. I've been working on
nock and that's the strategy we're using there.