Package development and classes in R

[hlapp]

From @DrK-Lo (see comments on #6):

I propose that we have time on the first day to talk about package development, classes in R, and how to use GitHub. Some of the people coming mentioned that they have not developed packages in R, and it's not clear to what extent people have used collaborative coding.

I've put the Github how-to into its own bootcamp idea (#10).