Switch back to after :all

Signed-off-by: Ken Barber <ken@bob.sh>
Improvements to example

* Change .rspec usage to pass the formatter in the Rake task.
* Fixed up Rakefile and added rspec:system rake task
* Stop rake being autorequired to avoid duplicate load issues
* Removed extraneous puts from tests
* Make sure 'yaml' is required in code that loads the configuration file.

Signed-off-by: Ken Barber <ken@bob.sh>