add support for superagent codegen

[prahaladbelavadi]

Ref: https://www.npmjs.com/package/superagent Github: github.com/ladjs/superagent Approach: Reproducing the pattern used for other nodejs generators like unirest and axios (already in the repository). Todo:

• [ ] Handle test cases
• [ ] Sanitize / clean up code from stray comments and code used for testing in local dev on the fly
• [ ] Get Feedback / Reviews
• [ ] Verify indentation and linting works as expected
• [ ] Verify that options are being supported
• [ ] Enquire if graphql support is absolutely necessary ?
• [ ] Find a Point of contact with Postman team to obtain reviews and cross check patterns / employed by the org
• [ ] Docs ?
• [ ] TimeLine ?
• [ ] Support ?
• [ ] Handoff ?
• [ ] Travis CI dependencies from Contributor doc
• [ ] Enquire if there's a way to test codegen / options with the postman native / web app