Implement a new csswring instance based API with per-instance preserveHacks and removeAllComments options.

  * csswring({preserveHacks: true, removeAllComments: true}).wring(css, {map: true});
  * postcss().use(csswring({preserveHacks: true, removeAllComments: true}).processor).process(css, {map: true});
  * csswring.wring(css, opts); now accepts preserveHacks and removeAllComments as options in addition to the postcss options.
Fix mistake in csswring.processor added by 0f055ba74.
Merge commit '1f7a92fbd120143846e98c768615686ac33b805e'

* commit '1f7a92fbd120143846e98c768615686ac33b805e':
  Specify a license with SPDX ID
  Version 0.2.1
  Test with `deepEqual()`
  Update dependencies
  Update keywords
Add tests for the new instance interface.
Rename .processor to `.postcss`

This matches the name that autoprefixer and all other postcss based libraries use.

For backwards compatibility `csswring.processor` is retained as an alias.
Merge pull request #8 from dantman/master

Implement a new csswring instance based API with per-instance  options.