runtime: Provide a real null object.
compiler: Use _monte.null instead of None.
runtime: Change true and false to be Monte-level objects.
compiler: Emit references to true and false instead of True and False.
Merge pull request #5 from MostAwesomeDude/bool-object

Bool objects
null object
oops
runtime: Fix `null != null` == false.

And reenable the test for it.