Added a rake task to run tests independent of the rails stack.
This is intended to allow us to pursue good architecture
(As per Uncle Bob's presentation) by putting most of our behavior
outside of the rails stack in PORO (plain old ruby objects) in the
form of interactors and business objects as much as possible.

To start and run this focused test suite instead of firing up the
entire rails test suite the new rake task is "test:focused"
executed with the full command line:
"bundle exec rake test:focused".