MF changes to plot.assoc.R and plot.assoc.Rd

Are you sure you used my master branch, not the one from your fork? Anyway, the change is in the commit, we need to get rid of it. One way is to run `git reset HEAD~` to undo the commit (preserving the changes), and then `git add -i` and `git commit`, so that you decide what changes go into the commit.