See #846 - moves CLI to a separate repository.

See #846 - moves CLI to a separate repository.

Moved to https://github.com/jakubpawlowicz/clean-css-cli

Why:

* At least 85% of top dependants use the API (see ticket) so
  removing CLI removes `commander` dependency for them;
* docs will be easier to follow as they describe API only;
* tests run 10x as fast since binary tests took 90% of time;
* CLI will be able to provide its own set of features which
  are not necessarilly provided or requred in API.

Drawbacks:

* It won't be straightforward to quickly test arbitrary CSS
  as binary is not available out of the box.