Make license-checker pipeline-friendly.

Warning: this is an opinionated PR.

Removes direct file writing options which make `license-checker` difficult to use within any kind of command-line processing pipeline.

* Will write only the formatted data to stdout using selected format: `--json` or `--csv`.
* Added an `--out` flag for approximating original behaviour. `--out` takes a destination path to write to.
* Removed coloured output by default from any file, json or csv output.
* Added docs to readme