Use headers from options.url if present
Use headers from options.url if present

As elsewhere in the code, options on the url argument take precedence
over options in the options argument.  Use the same logic for headers.

Signed-off-by: Kevin Locke <ffb4761cba839470133bee36aeb139f58d7dbaa9@kevinlocke.name>

kevinoid/swagger-spec-validator,kevinoid/swagger-spec-validator,kevinoid/swagger-spec-validator