FIXED: Bug in subterm_pos that was causing cyclic terms: unifications between
       Sub and Term would cause undesirable bindings in Term, and also is not
       desirable that Sub be unified arbitrarily with any free variable in Term.
       Proper handling of module qualified terms when the module match the
       context.
Merge pull request #10 from edisonm/master

FIXED: Bug in subterm_pos that was causing cyclic terms