1) changed default convergence difference
2) updated gitignore & rbuildignore
1) added model comparison top level function
2) for nrm: keep order or categories - fixes problems  with 'correct' definition in reshMG - because cpp functions rely on 'd' and 'recm' - so these two have to be in the same order.
3) changed reshMG for nelm to move the correct response in the first column
4) added RETURN to summary.nrm and summary.nelm
5) Changed reshMG documentation file