Ensure that the env config is not mutated after test

--FF & CW
Any test involving ENV['IHAT_URL'] was blowing up occasionally.
We were also unable to get a VCR cassette that would actually make Faraday throw a ConnectionFailed error, so we stubbed it. 
You could use [an around hook](https://relishapp.com/rspec/rspec-core/v/2-0/docs/hooks/around-hooks) here instead of separate before and after hooks.

The last time I did this, I had to run the example in a `begin; rescue; end` block. The example throws an exception when it's run, so the part of the around hook after the example runs wasn't executed. Verify that your around hook works even when the test fails or raises an exception.