feature/R

This pull request is incomplete!

I wrote these checkers while taking a Coursera class on R programming earlier this year.  The reason I never submitted the pull request was because I got stuck adding the test cases because they required R packages to be installed and I was unable to figure out how to do that with puppet.

In the time between adding these checkers and submitting this pull request I accidentally removed my original flycheck directory and apparently I had never commited the test cases so they have since been lost.  I can write them again but I will need help figuring out how to install those R packages and it looks like puppet is no longer used to manage test case dependencies?

I'm currently a bit constrained on time so expect my response time to be slow.
I think so: http://melpa.org/#/ess