IllegalArgumentException when using Optional

[cuzz22000]

When using Guava's Optional with a @QueryParam annotation the scanner does not recognize the object defining it as null producing the following exception.

io.federecio.dropwizard.junitrunner.DropwizardJunitRunnerException: java.lang.IllegalArgumentException: Unrecognized Type: [null]
    ...
Caused by: java.lang.IllegalArgumentException: Unrecognized Type: [null]
    at com.fasterxml.jackson.databind.type.TypeFactory._constructType(TypeFactory.java:405)
    at com.fasterxml.jackson.databind.type.TypeFactory.constructType(TypeFactory.java:354)
    at com.fasterxml.jackson.databind.ObjectMapper.constructType(ObjectMapper.java:1330)
    at com.wordnik.swagger.jackson.ModelResolver.resolveProperty(ModelResolver.java:62)
    ...

To reproduce the exception during unit tests I've added an Optional argument to io.federecio.dropwizard.swagger.TestResource.

 @GET
    @ApiOperation(OPERATION_DESCRIPTION)
    public Response dummyEndpoint(@QueryParam("dummy") final Optional<String> dummy) {
        return Response.ok().build();
    }

Branch containing the updated method can be found here -> https://github.com/TimeIncOSS/dropwizard-swagger/tree/optional-issue