[Jamie API] Driver API updates in 0.1.0.alpha19.

The long and the short of it is that each driver object now has a reference to its instance via `#instance`. Therefore, each action method no longer requires the `instance` parameter.

I also added timings for each instance action, so `Jamie::Driver#create` and `Jamie::Driver::destroy` will [output](https://github.com/jamie-ci/jamie/blob/80cd49285646acf28cc351686eaf0e42cd9cce8c/lib/jamie.rb#L679-L684) their elapsed time. One more bit of ceremony that can be trimmed out.

**Warning** I took a quick stab at updating the specs, but have not run them myself. I pledge to help though, if you need it :wink: