Support http://json-schema.org/draft-06/schema# or newer

[cobnett3]

Currently, this library seems to be built on draft-04.

jsonsubschema/jsonsubschema/config.py

Lines 16 to 22 in f6dbeb7

	# API to set which schema validator draft to use
	def set_json_validator_version(v=jsonschema.Draft4Validator):
	''' Currently, our subtype checking supports json schema draft 4 only,
	so VALIDATOR should not changed.
	We prodive the method for future support of other json schema versions. '''
	this.VALIDATOR = v

It would be great if it supports newer draft versions.

[cortadocodes]

Bumping this - it would be great to support the latest JSON metaschema (2020-12)

[shinnar]

This would be a great improvement, but I am not sure when/if the maintainers will have time to work on it.
If anyone is interested in submitting a PR for this, we would be happy to work with them and review/shepherd it.