adding R novice lessons that I started for NYU bootcamp

I made some novice-level R lessons for the NYU bootcamp last week. These are modeled on the new Python exercises for reading in data and building a program, and also borrow from some of the topics covered in the intermediate R lessons in the bc repo. The emphasis is on building programs and thinking modularly, as in other SWC lessons. They still need work, but might be a good starting point for others teaching R to novices. In our room, we got up to lesson 04, but there are probably a few places that we could have gone faster. Lesson 04 goes through R blocks, using the in development rblocks.R code, but this is also being developed as a package on github, so these lessons will need updating as the code develops.