code cleanup, jshint conformance
stripping trailing whitespace
Adding IMVU to the list of allowed predefined globals

This implementation will depend on IMVU.URI
Delegates to XMLHttpRequest if it supports CORS

- Added seam for dependency injection
- imvujs modularized
libxdr is now an XMLHttpRequest factory with CORS

- imvujs modularization
- imvujs unit test coverage
- Delegates to native XMLHttpRequest if supported

Notably missing:
- { anon: true } in constructor
- user, password arguments in .open()
- .open()'s async argument must not be false
- correct state changes: never gets to HEADERS_RECEIVED or LOADING
- property setter state assertions
- .upload property
- .responseType property
- .response property