ASDF error when attempting to run unit tests

[cwfoo]

README.txt says that (asdf:oos 'asdf:test-op '#:montezuma) runs the unit tests. However that immediately produces an ASDF error: :FORCE and :FORCE-NOT arguments not allowed in a nested call to ASDF/OPERATE:OPERATE unless identically to toplevel.

During compilation, a few other ASDF-related warnings and deprecation notices are printed. To prevent the error and to remove the warnings, montezuma.asd should be edited to conform to the conventions of ASDF version 3+.

I am using SBCL 2.0.1 and ASDF 3.3.4.

[luismbo]

@cwfoo would you like to prepare a pull request with your suggested fix?