Update to latest swagger-parser

[fehguy]

Description

There are a number of users having issues with codegen regarding relative references. There have been many upgrades in swagger-parser to address this--we need to update the parser version in codegen.

Swagger-codegen version

master

Swagger declaration file content or url

n/a

Command line used for generation

n/a

Steps to reproduce

n/a

Related issues

See swagger-api/swagger-parser#304