Added a gof.ergm method which masks the gof.ergm function in the ergm package. This makes the GOF output of ERGMs compatible with that of TERGMs.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/btergm@34 edb9625f-4e0d-4859-8d74-9fd3b1da38cb