Decode paths in error messages

The tool is very useful and less cryptic than json-schema-validator alone, but it would be nice if the tool "decoded" the more cryptic pointer embedded in error messages.

For example given the error response

{"loadingURI":"http://swagger.io/v2/schema.json#","pointer":"/definitions/responseValue"},"instance":{"pointer":"/paths/~1reports~1{reportId}~1content~1elements/get/responses/200"}}]

it would be nice if the validator "decoded' the pointer -- especially the ~1 encoding of slashes in the paths -- to and showed the path structure:

paths:
      "/reports/{reportid}/content/elements":
          get:
                responses: 
                     '200'

This would make it much easier to locate the source of the error in the input Swagger document.

Start by tracing how validator errors are formatted and where the instance pointer from the example is handled. Use the reported Swagger response to determine how JSON Pointer escaping such as ~1 should be decoded and represented as a readable path structure. Done means error messages show the decoded path clearly.