some fix in cell size check

corrected bug in size comparison, this was only designed for a 1D vector
data set in earlier version
new function for gofstat

This is a new function in the series of model comparison, it gives an
quick and dirty output of the goodness of fit statistics in xls file
format
allegedly I corrected some typos on this one

just a few corrections...
Simple tidy up on text. No formal testing. Assume OK. Closes pull request #2