Previously, it was a publically accessible but invalid value (valueEmpty).
* Deprecate internal use of UndefinedValue(), NullValue(), FalseValue(), TrueValue()
* Guard against Empty, Result, Reference values from escaping the package
* Faster, more straightforward, etc.
* More advanced object literals (get ..., set ...)
* More tests using JavaScript from the wild (http://cdnjs.com/)