Various snippet generation issues

[erunion]

https://github.com/readmeio/api-explorer/blob/master/example/swagger-files/petstore.json#L135-L172

sdk.get('/v2/pet/findByTags', {tags: 'tags', accept: 'application/xml', authorization: 'Bearer 123'})
  .then(res => res.json())
  .then(res => {
    console.log(res);
  });

• Does not support operation IDs right now.
• Should not bother adding Accept headers that are implied by the request body type. The api module should automatically handle these (or let it fall through to @readme/oas-to-har.
• Auth keys should be put into .auth() instead of as headers.