Tries to add the feature asked in issue #19. Currently not sure how to name
the .exercism file and it was left as-in. The user will can choose to store
configuration in ~/.exercism or ~/.config/exercism/.exercism.

The path ~/.config/exercism seems appropiate perhaps for storing other information
pertinent to exorcism.
Changed alternate path from ~/.config/exercism/.exercism to ~/.config/.exercism
bit more guidance when choosing location to store config file
Refactor config