Add scenario covering template generation

The workaround code in the background to this scenario will go once we
remove the Rails detection code and support recursive directory
processing.
Recursively process directories with .dice files

This removes the previously deprecated functionality but adds full
recursive directory descent with scenario coverage. Only files with the
'.dice' extension will be processed.

This is a minimally invasive set of changes. More refactoring is
probably possible but I've left this asside to get the new functionality
up and running as quickly as possible.
Add scenarios covering custom template providers
Merge pull request #51 from mdsol/feature/recursive_directory_processing

Recursive directory processing, removal of deprecated features