Allows you to build and store services.

Service class validates and builds docker services.
Repo class is used for pushing/pulling tagged docker images.
Setup up a basic CLI. Has an CLIProject class that loads in the configuration
(skipper.yml) and loads in the creds (.skippercfg).
Added a basic logger.

New command.
`skipper build [SERVICE(s)]`
allows you to build/upload services.

Closes #16