Excel-REST v4.0.0 RC

Some fun changes coming to Excel-REST v4.0.0!

- [x] Switch to `WinHttpRequest` (Modern alternative to `ServerXMLHTTP`)
- [x] "Freeze" `Request` on execute (multiple requests with same `Request` don't interact)
- [x] Allow user-specified `Body` converter and `Response` parser (see #43 and #61)
- [x] Remove deprecated code
- [x] Add large string support to JSON (see #62)
- [x] General VBA compatibility
- [x] Add Mac Support
- [x] Separate Async behavior into separate Class
- [x] Allow duplicate keys in querystring params (see #68 and investigate converting params too)
- [x] Update installer (for Mac and Windows)
- [x] Formalize and check error messages and numbers
- [x] Rename GitHub project to VBA-tools/VBA-Web
- [x] Release RC

Deferred to RC (new branch)
- Update authenticators (ensure Mac support)
- Docs and Examples: POST, SOAP, and docs/example website
- Detailed transition guide