Roxygenize to set C sorting of family-generated documentation
Don't use a factor for ID column if .id parameter is not set in ldply() and rdply()

This is to ensure backward compatibility with the many packages that depend on plyr, e.g., ggplot2
Roxygenize
Merge pull request #195 from krlmlr/id-na

Don't use a factor for ID column if .id parameter is not set in ldply() and rdply()