Fixed the way roots of a fourtech object are computed.  Now we construct a chebtech2 object from the fourtech object and use its roots command.
Fixed the way roots of a fourtech object are computed.  Now we construct a chebtech2 object from the fourtech object and use its roots command.

alshedivat/chebfun,asgeirbirkis/chebfun,ilovejs/chebfun