support for JSON pointers

[kinlane]

• I’d add support for JSON pointers, to allow for some reuse and separation:

"urls": [
{
"type": "signup",
"url": "https://sendgrid.com/docs/API_Reference/SMTP_API/index.html"
},
{
“$ref”: “http://foo.com/myApi”
}
],

** From email with Tony