improving coverage of launcher integration test

vapp_spec used to test only the model and fog_service layer. refactored
it to do following things
- accept data from yaml file
- building yaml file in runtime by importing data from users environment
  variables
- integration test now test everything except the cli. cli is already
  being tested using cucumber features
- this should help us catch bugs in core tool layer.
Merge pull request #59 from alphagov/improving_coverage_of_integration_test

improving coverage of launcher integration test