Add Specs

- Integrate [Excel-TDD](https://github.com/timhall/Excel-TDD) to fully test Excel-REST library
- Handle timeouts for sync and async requests
- Remove reference dependencies and use `CreateObject` instead
- Add cachebreaker as querystring param only
- Add `Join` helpers to resolve double-slash issue between base and resource url
- Only add "?" for querystring if querystring will be created and "?" isn't present
- Only put parameters in body if there are parameters