Fix missing test framework

**As a** developer 
**In order to** prevent dramas 
**And** to learn about modules testing 
**I want** the gem to contain a decent set of tests before its v1.0.0 is released 

More concretely: 
**Given** I am using RSpec within a dummy app to test the gem behaviour 
**In order to** be able to test more than one feature 
**I want** to be able to modify the dummy app setup programatically 

As exposed in #1, I would like to be able to express gem use cases as Cucumber features, use Aruba to set the dummy app up and demonstrate the gem behaviour for each use case with RSpec. That would ensure both the gem testing and a kind of practical documentation.