Make faraday hook disableable.
Add a pending spec foor an integration bug w/ typhoeus/faraday.

I believe this is a bug in typhoeus.  I've submitted
a PR with a failing spec to typhoeus for this:

https://github.com/typhoeus/typhoeus/pull/324

For now, the best we can do here is a pending spec.

Fixes #299.
Merge pull request #339 from vcr/issue-299

Issue 299