add .ruby-version file

For rubyenv and chruby to pick up
add new empty backlog
add better test config

- expose mock method
- Turn config to be more informative when encountering errors
add shovel items into a backlog
use a user_story object for backlog item mock
add backlog title to the constructor
add backlog refinement: add pbi's to the backlog
add Epicable behaviour

- Epicable duck type found
- Epicable interface tests
- Backlog#epics collection
add ability to breakdown epics in backlog