changes to docs needed to satisfy R CMD CHECK

these are mostly related to the fact that I thought I had to
document the .RData files included with the package, which is
not correct; the objects within the .RData files need to be
documented.
changes related to NAMESPACE resulting from satisfying R CMD CHECK
fixed typo in docs

used to say total.popn.size instead of total.pop.size
changes to docs for data included with packages

these came up when I tried to satisfy the checks performed by
R CMD CHECK
unparse.trait now has default sep of "." instead of "\\."
renamed mean.ties.truth to compare.mean.ties.truth

I believe R CMD CHECK complained about the old name because it
looked like it was an S3-dispatched version of mean() for objects
of class 'ties.truth', which makes no sense
renamed sum.degree.estimator to summation.degree.estimator

I believe R CMD CHECK was complaining about the old name b/c it looks
like a version of the sum() method for S3 objects of class
'degree.estimator'