Middleware registration for Faraday 0.7.

Why? Because it's such a simple change. If it was much more work than this, I'd probably just stick with 0.8 and 0.9.
Updating Faraday version dependency.

Presuming 0.9 was excluded in the refactor, and then this got missed in my recent patch.
Connection helper method shouldn't use Faraday's own path.

Overwriting files in the load path of other gems is a receipe for confusion and frustration.
Merge pull request #4 from pat/multi-version

Faraday 0.7-0.9 support