Add some resources on "outside in" testing

[newswim]

This is something quite popular within the Rails community, particular following the TDD trends at Thoughtbot. Creating this placeholder issue as a dumping ground for "Outside-In" related content.

• TDD - From the Inside Out or the Outside In?
• Outside-In TDD (NebraskaJS talk)

Not this technique might also be referred to as Bottom Up, Chicago School, or Classic Approach.

[Junaidsahi]

Xxtw, 56744---&$$++()976dfggvlours!! #145