Edits to make novice R lesson 01 more similar to novice Python lesson 01.

I have made edits so that the first R lesson more closely follows the Python lesson. It covers all the same topics save two:

  + Loading external packages - omitted because none of the operations in the lesson require loading an external package.
  + How to display three plots side-by-side - omitted because this is more complicated in R. This would require discussing how to set and reset `par` options, which is not a beginner topic.

Here's how you can quickly compare the two rendered files:

```
# clone bc repo
git clone git@github.com:swcarpentry/bc.git
# create and switch to new branch
git checkout -b review-pr
# add remote
git remote add jdb git@github.com:jdblischak/bc.git
# pull changes from my branch
git pull jdb 01-starting-with-data
# build site locally
make site
```
Then compare the rendered files  `_site/novice/r/01-starting-with-data.html` and `_site/novice/python/01-numpy.html`.
@jdblischak Actually I'm agnostic how people create the `.R` file in the first place or open it (as long as they don't start RStudio and then use `File` > `Open`) otherwise we have either to get people used to using `setwd()` *or* use a GUI tool which I'm uncomfortable with as you make people dependent upon that particular GUI (note I'm not singling RStudio out here - any GUI interface has this problem).

As most BCs have to have shell as a component, perhaps shell could come first in the lesson plan, by which time they'll know `touch` etc and launching R/RStudio from the shell? Plus they'll know some more about paths and relative paths etc which will help then with `setwd()`.

I am also conscious that this is a novice lesson. We can't include everything. But ingraining `setwd()` or use of a GUI tool from the very get go seems counter to the concepts that we wish to get across to people by teaching them shell, programming, VC etc.