change topo_module.f90 so that it only gives a warning if the topo fails to cover the domain by less than 1%, which might be due to lack of precision in cellsize, for example when using topo_type 2 or 3.
Merge pull request #104 from rjleveque/topo_domain_warning

change topo_module.f90 so that it only gives a warning if the topo fails to cover the domain...