Validate Postman Input and Outut

[philsturgeon]

Using JSON Schema parser to validate that examples for postman collection are valid for its v2 schema.

The main commit here is https://github.com/luckymarmot/API-Flow/pull/154/commits/d304d4b4758b6d668bf862e328ea40868f4b71d9, but I have a bunch of changes in my own branch. If you want this change and you want it clean, let me know and I'll clean it up, but I've not heard anything back on my other PRs.

Next steps:

• Ensure Swagger examples are also following the official OpenAPI v2 JSON Schema file: https://github.com/OAI/OpenAPI-Specification/tree/master/schemas/v2.0
• When OpenAPI v3.0 JSON Schema is finished (https://github.com/OAI/OpenAPI-Specification/pull/1236 or https://github.com/OAI/OpenAPI-Specification/pull/1270) we can validate that too