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Features:
* Detailed and verbose output format options
Breaking changes:
* JSONSchema.validate() now returns a Scope result object
Bug fixes:
* Fixed the instance location (shown in output) for object keys evaluated by "propertyNames"
Miscellaneous:
* Failing schema nodes no longer have error messages, and are excluded from basic output
* A Scope.passed property indicates a scope's assertion result, while Scope.valid indicates its
validation result (these can only differ for an "if" keyword subscope)
* Improved the API (used by keywords) and internal structure of the Scope class
* Dropped the Annotation and Error classes